dt-bindings: iio: adc: stm32-adc: convert bindings to json-schema

Convert the STM32 ADC binding to DT schema format using json-schema
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt

-STMicroelectronics STM32 ADC device driver
-
-STM32 ADC is a successive approximation analog-to-digital converter.
-It has several multiplexed input channels. Conversions can be performed
-in single, continuous, scan or discontinuous mode. Result of the ADC is
-stored in a left-aligned or right-aligned 32-bit data register.
-Conversions can be launched in software or using hardware triggers.
-
-The analog watchdog feature allows the application to detect if the input
-voltage goes beyond the user-defined, higher or lower thresholds.
-
-Each STM32 ADC block can have up to 3 ADC instances.
-
-Each instance supports two contexts to manage conversions, each one has its
-own configurable sequence and trigger:
-- regular conversion can be done in sequence, running in background
-- injected conversions have higher priority, and so have the ability to
-  interrupt regular conversion sequence (either triggered in SW or HW).
-  Regular sequence is resumed, in case it has been interrupted.
-
-Contents of a stm32 adc root node:
------------------------------------
-Required properties:
-- compatible: Should be one of:
-  "st,stm32f4-adc-core"
-  "st,stm32h7-adc-core"
-  "st,stm32mp1-adc-core"
-- reg: Offset and length of the ADC block register set.
-- interrupts: One or more interrupts for ADC block. Some parts like stm32f4
-  and stm32h7 share a common ADC interrupt line. stm32mp1 has two separate
-  interrupt lines, one for each ADC within ADC block.
-- clocks: Core can use up to two clocks, depending on part used:
-  - "adc" clock: for the analog circuitry, common to all ADCs.
-    It's required on stm32f4.
-    It's optional on stm32h7.
-  - "bus" clock: for registers access, common to all ADCs.
-    It's not present on stm32f4.
-    It's required on stm32h7.
-- clock-names: Must be "adc" and/or "bus" depending on part used.
-- interrupt-controller: Identifies the controller node as interrupt-parent
-- vdda-supply: Phandle to the vdda input analog voltage.
-- vref-supply: Phandle to the vref input analog reference voltage.
-- #interrupt-cells = <1>;
-- #address-cells = <1>;
-- #size-cells = <0>;
-
-Optional properties:
-- A pinctrl state named "default" for each ADC channel may be defined to set
-  inX ADC pins in mode of operation for analog input on external pin.
-- booster-supply: Phandle to the embedded booster regulator that can be used
-  to supply ADC analog input switches on stm32h7 and stm32mp1.
-- vdd-supply: Phandle to the vdd input voltage. It can be used to supply ADC
-  analog input switches on stm32mp1.
-- st,syscfg: Phandle to system configuration controller. It can be used to
-  control the analog circuitry on stm32mp1.
-- st,max-clk-rate-hz: Allow to specify desired max clock rate used by analog
-  circuitry.
-
-Contents of a stm32 adc child node:
------------------------------------
-An ADC block node should contain at least one subnode, representing an
-ADC instance available on the machine.
-
-Required properties:
-- compatible: Should be one of:
-  "st,stm32f4-adc"
-  "st,stm32h7-adc"
-  "st,stm32mp1-adc"
-- reg: Offset of ADC instance in ADC block (e.g. may be 0x0, 0x100, 0x200).
-- clocks: Input clock private to this ADC instance. It's required only on
-  stm32f4, that has per instance clock input for registers access.
-- interrupts: IRQ Line for the ADC (e.g. may be 0 for adc@0, 1 for adc@100 or
-  2 for adc@200).
-- st,adc-channels: List of single-ended channels muxed for this ADC.
-  It can have up to 16 channels on stm32f4 or 20 channels on stm32h7, numbered
-  from 0 to 15 or 19 (resp. for in0..in15 or in0..in19).
-- st,adc-diff-channels: List of differential channels muxed for this ADC.
-  Depending on part used, some channels can be configured as differential
-  instead of single-ended (e.g. stm32h7). List here positive and negative
-  inputs pairs as <vinp vinn>, <vinp vinn>,... vinp and vinn are numbered
-  from 0 to 19 on stm32h7)
-  Note: At least one of "st,adc-channels" or "st,adc-diff-channels" is required.
-  Both properties can be used together. Some channels can be used as
-  single-ended and some other ones as differential (mixed). But channels
-  can't be configured both as single-ended and differential (invalid).
-- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers" in
-  Documentation/devicetree/bindings/iio/iio-bindings.txt
-
-Optional properties:
-- dmas: Phandle to dma channel for this ADC instance.
-  See ../../dma/dma.txt for details.
-- dma-names: Must be "rx" when dmas property is being used.
-- assigned-resolution-bits: Resolution (bits) to use for conversions. Must
-  match device available resolutions:
-  * can be 6, 8, 10 or 12 on stm32f4
-  * can be 8, 10, 12, 14 or 16 on stm32h7
-  Default is maximum resolution if unset.
-- st,min-sample-time-nsecs: Minimum sampling time in nanoseconds.
-  Depending on hardware (board) e.g. high/low analog input source impedance,
-  fine tune of ADC sampling time may be recommended.
-  This can be either one value or an array that matches 'st,adc-channels' list,
-  to set sample time resp. for all channels, or independently for each channel.
-
-Example:
-	adc: adc@40012000 {
-		compatible = "st,stm32f4-adc-core";
-		reg = <0x40012000 0x400>;
-		interrupts = <18>;
-		clocks = <&rcc 0 168>;
-		clock-names = "adc";
-		vref-supply = <&reg_vref>;
-		interrupt-controller;
-		pinctrl-names = "default";
-		pinctrl-0 = <&adc3_in8_pin>;
-
-		#interrupt-cells = <1>;
-		#address-cells = <1>;
-		#size-cells = <0>;
-
-		adc@0 {
-			compatible = "st,stm32f4-adc";
-			#io-channel-cells = <1>;
-			reg = <0x0>;
-			clocks = <&rcc 0 168>;
-			interrupt-parent = <&adc>;
-			interrupts = <0>;
-			st,adc-channels = <8>;
-			dmas = <&dma2 0 0 0x400 0x0>;
-			dma-names = "rx";
-			assigned-resolution-bits = <8>;
-		};
-		...
-		other adc child nodes follow...
-	};
-
-Example to setup:
-- channel 1 as single-ended
-- channels 2 & 3 as differential (with resp. 6 & 7 negative inputs)
-
-	adc: adc@40022000 {
-		compatible = "st,stm32h7-adc-core";
-		...
-		adc1: adc@0 {
-			compatible = "st,stm32h7-adc";
-			...
-			st,adc-channels = <1>;
-			st,adc-diff-channels = <2 6>, <3 7>;
-		};
-	};