dt-bindings: adc: add AD7173

The AD7173 family offer a complete integrated Sigma-Delta ADC solution
which can be used in high precision, low noise single channel applications
or higher speed multiplexed applications. The Sigma-Delta ADC is intended
primarily for measurement of signals close to DC but also delivers
outstanding performance with input bandwidths out to ~10kHz.
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
Link: https://lore.kernel.org/r/20240228110622.25114-1-mitrutzceclan@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2023 Analog Devices Inc.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,ad7173.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices AD7173 ADC
+
+maintainers:
+  - Ceclan Dumitru <dumitru.ceclan@analog.com>
+
+description: |
+  Analog Devices AD717x ADC's:
+  The AD717x family offer a complete integrated Sigma-Delta ADC solution which
+  can be used in high precision, low noise single channel applications
+  (Life Science measurements) or higher speed multiplexed applications
+  (Factory Automation PLC Input modules). The Sigma-Delta ADC is intended
+  primarily for measurement of signals close to DC but also delivers
+  outstanding performance with input bandwidths out to ~10kHz.
+
+  Datasheets for supported chips:
+    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7172-2.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7173-8.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7175-2.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7176-2.pdf
+
+properties:
+  compatible:
+    enum:
+      - adi,ad7172-2
+      - adi,ad7173-8
+      - adi,ad7175-2
+      - adi,ad7176-2
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    minItems: 1
+    items:
+      - description: |
+          Ready: multiplexed with SPI data out. While SPI CS is low,
+          can be used to indicate the completion of a conversion.
+
+      - description: |
+          Error: The three error bits in the status register (ADC_ERROR, CRC_ERROR,
+          and REG_ERROR) are OR'ed, inverted, and mapped to the ERROR pin.
+          Therefore, the ERROR pin indicates that an error has occurred.
+
+  interrupt-names:
+    minItems: 1
+    items:
+      - const: rdy
+      - const: err
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+  spi-max-frequency:
+    maximum: 20000000
+
+  gpio-controller:
+    description: Marks the device node as a GPIO controller.
+
+  '#gpio-cells':
+    const: 2
+    description:
+      The first cell is the GPIO number and the second cell specifies
+      GPIO flags, as defined in <dt-bindings/gpio/gpio.h>.
+
+  vref-supply:
+    description: |
+      Differential external reference supply used for conversion. The reference
+      voltage (Vref) specified here must be the voltage difference between the
+      REF+ and REF- pins: Vref = (REF+) - (REF-).
+
+  vref2-supply:
+    description: |
+      Differential external reference supply used for conversion. The reference
+      voltage (Vref2) specified here must be the voltage difference between the
+      REF2+ and REF2- pins: Vref2 = (REF2+) - (REF2-).
+
+  avdd-supply:
+    description: Avdd supply, can be used as reference for conversion.
+                 This supply is referenced to AVSS, voltage specified here
+                 represents (AVDD1 - AVSS).
+
+  avdd2-supply:
+    description: Avdd2 supply, used as the input to the internal voltage regulator.
+                 This supply is referenced to AVSS, voltage specified here
+                 represents (AVDD2 - AVSS).
+
+  iovdd-supply:
+    description: iovdd supply, used for the chip digital interface.
+
+  clocks:
+    maxItems: 1
+    description: |
+      Optional external clock source. Can include one clock source: external
+      clock or external crystal.
+
+  clock-names:
+    enum:
+      - ext-clk
+      - xtal
+
+  '#clock-cells':
+    const: 0
+
+patternProperties:
+  "^channel@[0-9a-f]$":
+    type: object
+    $ref: adc.yaml
+    unevaluatedProperties: false
+
+    properties:
+      reg:
+        minimum: 0
+        maximum: 15
+
+      diff-channels:
+        items:
+          minimum: 0
+          maximum: 31
+
+      adi,reference-select:
+        description: |
+          Select the reference source to use when converting on
+          the specific channel. Valid values are:
+          vref       : REF+  /REF−
+          vref2      : REF2+ /REF2−
+          refout-avss: REFOUT/AVSS (Internal reference)
+          avdd       : AVDD  /AVSS
+
+          External reference ref2 only available on ad7173-8.
+          If not specified, internal reference used.
+        $ref: /schemas/types.yaml#/definitions/string
+        enum:
+          - vref
+          - vref2
+          - refout-avss
+          - avdd
+        default: refout-avss
+
+    required:
+      - reg
+      - diff-channels
+
+required:
+  - compatible
+  - reg
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+  - if:
+      properties:
+        compatible:
+          not:
+            contains:
+              const: adi,ad7173-8
+    then:
+      properties:
+        vref2-supply: false
+      patternProperties:
+        "^channel@[0-9a-f]$":
+          properties:
+            adi,reference-select:
+              enum:
+                - vref
+                - refout-avss
+                - avdd
+            reg:
+              maximum: 3
+
+  - if:
+      anyOf:
+        - required: [clock-names]
+        - required: [clocks]
+    then:
+      properties:
+        '#clock-cells': false
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    spi {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      adc@0 {
+        compatible = "adi,ad7173-8";
+        reg = <0>;
+
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        interrupts = <25 IRQ_TYPE_EDGE_FALLING>;
+        interrupt-names = "rdy";
+        interrupt-parent = <&gpio>;
+        spi-max-frequency = <5000000>;
+        gpio-controller;
+        #gpio-cells = <2>;
+        #clock-cells = <0>;
+
+        vref-supply = <&dummy_regulator>;
+
+        channel@0 {
+          reg = <0>;
+          bipolar;
+          diff-channels = <0 1>;
+          adi,reference-select = "vref";
+        };
+
+        channel@1 {
+          reg = <1>;
+          diff-channels = <2 3>;
+        };
+
+        channel@2 {
+          reg = <2>;
+          bipolar;
+          diff-channels = <4 5>;
+        };
+
+        channel@3 {
+          reg = <3>;
+          bipolar;
+          diff-channels = <6 7>;
+        };
+
+        channel@4 {
+          reg = <4>;
+          diff-channels = <8 9>;
+          adi,reference-select = "avdd";
+        };
+      };
+    };