dt-bindings: iio: adc: add adi,ad7780.yaml binding

* Analog Devices AD7170/AD7171/AD7780/AD7781

Data sheets:

- AD7170:

	* https://www.analog.com/media/en/technical-documentation/data-sheets/AD7170.pdf

- AD7171:

	* https://www.analog.com/media/en/technical-documentation/data-sheets/AD7171.pdf

- AD7780:

	* https://www.analog.com/media/en/technical-documentation/data-sheets/ad7780.pdf

- AD7781:

	* https://www.analog.com/media/en/technical-documentation/data-sheets/AD7781.pdf

Required properties:

- compatible: should be one of

	* "adi,ad7170"

	* "adi,ad7171"

	* "adi,ad7780"

	* "adi,ad7781"

- reg: spi chip select number for the device

- vref-supply: the regulator supply for the ADC reference voltage

Optional properties:

- powerdown-gpios:  must be the device tree identifier of the PDRST pin. If

		    specified, it will be asserted during driver probe. As the

		    line is active high, it should be marked GPIO_ACTIVE_HIGH.

- adi,gain-gpios:   must be the device tree identifier of the GAIN pin. Only for

		    the ad778x chips. If specified, it will be asserted during

		    driver probe. As the line is active low, it should be marked

		    GPIO_ACTIVE_LOW.

- adi,filter-gpios: must be the device tree identifier of the FILTER pin. Only

		    for the ad778x chips. If specified, it will be asserted

		    during driver probe. As the line is active low, it should be

		    marked GPIO_ACTIVE_LOW.

Example:

adc@0 {

	compatible =  "adi,ad7780";

	reg =	      <0>;

	vref-supply = <&vdd_supply>

	powerdown-gpios  = <&gpio 12 GPIO_ACTIVE_HIGH>;

	adi,gain-gpios   = <&gpio  5 GPIO_ACTIVE_LOW>;

	adi,filter-gpios = <&gpio 15 GPIO_ACTIVE_LOW>;

};

# SPDX-License-Identifier: GPL-2.0

%YAML 1.2

---

$id: http://devicetree.org/schemas/iio/adc/adi,ad7780.yaml#

$schema: http://devicetree.org/meta-schemas/core.yaml#

title: Analog Devices AD7170/AD7171/AD7780/AD7781 analog to digital converters

maintainers:

  - Michael Hennerich <michael.hennerich@analog.com>

description: |

  The ad7780 is a sigma-delta analog to digital converter. This driver provides

  reading voltage values and status bits from both the ad778x and ad717x series.

  Its interface also allows writing on the FILTER and GAIN GPIO pins on the

  ad778x.

  Specifications on the converters can be found at:

    AD7170:

      https://www.analog.com/media/en/technical-documentation/data-sheets/AD7170.pdf

    AD7171:

      https://www.analog.com/media/en/technical-documentation/data-sheets/AD7171.pdf

    AD7780:

      https://www.analog.com/media/en/technical-documentation/data-sheets/ad7780.pdf

    AD7781:

      https://www.analog.com/media/en/technical-documentation/data-sheets/AD7781.pdf

properties:

  compatible:

    enum:

      - adi,ad7170

      - adi,ad7171

      - adi,ad7780

      - adi,ad7781

  reg:

    maxItems: 1

  avdd-supply:

    description:

      The regulator supply for the ADC reference voltage.

    maxItems: 1

  powerdown-gpios:

    description:

      Must be the device tree identifier of the PDRST pin. If

      specified, it will be asserted during driver probe. As the

      line is active high, it should be marked GPIO_ACTIVE_HIGH.

    maxItems: 1

  adi,gain-gpios:

    description:

      Must be the device tree identifier of the GAIN pin. Only for

      the ad778x chips. If specified, it will be asserted during

      driver probe. As the line is active low, it should be marked

      GPIO_ACTIVE_LOW.

    maxItems: 1

  adi,filter-gpios:

    description:

      Must be the device tree identifier of the FILTER pin. Only

      for the ad778x chips. If specified, it will be asserted

      during driver probe. As the line is active low, it should be

      marked GPIO_ACTIVE_LOW.

    maxItems: 1

required:

  - compatible

  - reg

examples:

  - |

    #include <dt-bindings/gpio/gpio.h>

    spi0 {

        #address-cells = <1>;

        #size-cells = <0>;

        adc@0 {

            compatible = "adi,ad7780";

            reg = <0>;

            avdd-supply      = <&vdd_supply>;

            powerdown-gpios  = <&gpio0 12 GPIO_ACTIVE_HIGH>;

            adi,gain-gpios   = <&gpio1  5 GPIO_ACTIVE_LOW>;

            adi,filter-gpios = <&gpio2 15 GPIO_ACTIVE_LOW>;

        };

    };