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

This patch adds a YAML binding for the Analog Devices AD7780/1 and
AD7170/1 analog-to-digital converters.
Signed-off-by: Renato Lui Geh <renatogeh@gmail.com>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/adi,ad7780.txt

-* 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>;
-};

Documentation/devicetree/bindings/iio/adc/adi,ad7780.yaml

+# 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>;
+        };
+    };