dt-bindings: iio: dfsdm: move to backend framework

Change the DFSDM binding to use the new IIO backend framework,
along with the adoption of IIO generic channels.
This binding change allows to add scaling support to the DFSDM.

Keep the legacy binding as deprecated for backward compatibility.

The io-backends property is supported only in generic IIO channel
binding.

- Channel description with the generic binding (Audio and Analog):

  Properties superseded by generic properties:
    st,adc-channels: becomes "reg" property in channel node
    st,adc-channel-names: becomes "label" property in channel node
  Properties moved to channel child node:
    st,adc-channel-types: becomes st,adc-channel-type
    st,adc-channel-clk-src, st,adc-alt-channel

- Analog binding:

  DFSDM filter channel is configured as an IIO backend consumer.
  Add io-backends property in channel child nodes.

  DFSDM is no more configured as a channel consumer from SD modulator.
  Use of io-channels in DFSDM node is deprecated.

- Audio binding:

  DFSDM audio DAI is configured as a channel consumer from DFSDM filter.
  No change compare to legacy.
Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20240730084640.1307938-5-olivier.moysan@foss.st.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml

@@ -102,9 +102,11 @@ patternProperties:
         items:
           minimum: 0
           maximum: 7
+        deprecated: true
 
       st,adc-channel-names:
         description: List of single-ended channel names.
+        deprecated: true
 
       st,filter-order:
         description: |
@@ -118,6 +120,12 @@ patternProperties:
       "#io-channel-cells":
         const: 1
 
+      '#address-cells':
+        const: 1
+
+      '#size-cells':
+        const: 0
+
       st,adc-channel-types:
         description: |
           Single-ended channel input type.
@@ -128,6 +136,7 @@ patternProperties:
         items:
           enum: [ SPI_R, SPI_F, MANCH_R, MANCH_F ]
         $ref: /schemas/types.yaml#/definitions/non-unique-string-array
+        deprecated: true
 
       st,adc-channel-clk-src:
         description: |
@@ -139,6 +148,7 @@ patternProperties:
         items:
           enum: [ CLKIN, CLKOUT, CLKOUT_F, CLKOUT_R ]
         $ref: /schemas/types.yaml#/definitions/non-unique-string-array
+        deprecated: true
 
       st,adc-alt-channel:
         description:
@@ -147,6 +157,7 @@ patternProperties:
           If not set, channel n is connected to SPI input n.
           If set, channel n is connected to SPI input n + 1.
         type: boolean
+        deprecated: true
 
       st,filter0-sync:
         description:
@@ -165,11 +176,60 @@ patternProperties:
       - compatible
       - reg
       - interrupts
-      - st,adc-channels
-      - st,adc-channel-names
       - st,filter-order
       - "#io-channel-cells"
 
+    patternProperties:
+      "^channel@[0-7]$":
+        type: object
+        $ref: adc.yaml
+        unevaluatedProperties: false
+        description: Represents the external channels which are connected to the DFSDM.
+
+        properties:
+          reg:
+            maximum: 7
+
+          label:
+            description:
+              Unique name to identify which channel this is.
+
+          st,adc-channel-type:
+            description: |
+              Single-ended channel input type.
+              - "SPI_R": SPI with data on rising edge (default)
+              - "SPI_F": SPI with data on falling edge
+              - "MANCH_R": manchester codec, rising edge = logic 0, falling edge = logic 1
+              - "MANCH_F": manchester codec, rising edge = logic 1, falling edge = logic 0
+            $ref: /schemas/types.yaml#/definitions/string
+            enum: [ SPI_R, SPI_F, MANCH_R, MANCH_F ]
+
+          st,adc-channel-clk-src:
+            description: |
+              Conversion clock source.
+              - "CLKIN": external SPI clock (CLKIN x)
+              - "CLKOUT": internal SPI clock (CLKOUT) (default)
+              - "CLKOUT_F": internal SPI clock divided by 2 (falling edge).
+              - "CLKOUT_R": internal SPI clock divided by 2 (rising edge).
+            $ref: /schemas/types.yaml#/definitions/string
+            enum: [ CLKIN, CLKOUT, CLKOUT_F, CLKOUT_R ]
+
+          st,adc-alt-channel:
+            description:
+              Must be defined if two sigma delta modulators are
+              connected on same SPI input.
+              If not set, channel n is connected to SPI input n.
+              If set, channel n is connected to SPI input n + 1.
+            type: boolean
+
+          io-backends:
+            description:
+              Used to pipe external sigma delta modulator or internal ADC backend to DFSDM channel.
+            maxItems: 1
+
+        required:
+          - reg
+
     allOf:
       - if:
           properties:
@@ -199,10 +259,20 @@ patternProperties:
               description:
                 From common IIO binding. Used to pipe external sigma delta
                 modulator or internal ADC output to DFSDM channel.
+              deprecated: true
 
+          if:
+            required:
+              - st,adc-channels
+          then:
             required:
               - io-channels
 
+          patternProperties:
+            "^channel@[0-7]$":
+              required:
+                - io-backends
+
       - if:
           properties:
             compatible:
@@ -298,6 +368,7 @@ examples:
       #address-cells = <1>;
       #size-cells = <0>;
 
+      // Example 1: Audio use case with generic binding
       dfsdm0: filter@0 {
         compatible = "st,stm32-dfsdm-dmic";
         reg = <0>;
@@ -305,12 +376,18 @@ examples:
         dmas = <&dmamux1 101 0x400 0x01>;
         dma-names = "rx";
         #io-channel-cells = <1>;
-        st,adc-channels = <1>;
-        st,adc-channel-names = "dmic0";
-        st,adc-channel-types = "SPI_R";
-        st,adc-channel-clk-src = "CLKOUT";
+        #address-cells = <1>;
+        #size-cells = <0>;
         st,filter-order = <5>;
 
+        channel@1 {
+          reg = <1>;
+          label = "dmic0";
+          st,adc-channel-type = "SPI_R";
+          st,adc-channel-clk-src = "CLKOUT";
+          st,adc-alt-channel;
+        };
+
         asoc_pdm0: dfsdm-dai {
           compatible = "st,stm32h7-dfsdm-dai";
           #sound-dai-cells = <0>;
@@ -318,19 +395,34 @@ examples:
         };
       };
 
-      dfsdm_pdm1: filter@1 {
+      // Example 2: Analog use case with generic binding
+      dfsdm1: filter@1 {
         compatible = "st,stm32-dfsdm-adc";
         reg = <1>;
         interrupts = <GIC_SPI 111 IRQ_TYPE_LEVEL_HIGH>;
         dmas = <&dmamux1 102 0x400 0x01>;
         dma-names = "rx";
-        #io-channel-cells = <1>;
-        st,adc-channels = <2 3>;
-        st,adc-channel-names = "in2", "in3";
-        st,adc-channel-types = "SPI_R", "SPI_R";
-        st,adc-channel-clk-src = "CLKOUT_F", "CLKOUT_F";
-        io-channels = <&sd_adc2 &sd_adc3>;
         st,filter-order = <1>;
+        #io-channel-cells = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        channel@2 {
+          reg = <2>;
+          label = "in2";
+          st,adc-channel-type = "SPI_F";
+          st,adc-channel-clk-src = "CLKOUT";
+          st,adc-alt-channel;
+          io-backends = <&sd_adc2>;
+        };
+
+        channel@3 {
+          reg = <3>;
+          label = "in3";
+          st,adc-channel-type = "SPI_R";
+          st,adc-channel-clk-src = "CLKOUT";
+          io-backends = <&sd_adc3>;
+        };
       };
     };