dt-bindings: iio: dac: Add docs for AD5770R DAC

Adding dt-bindings documentation for AD5770R DAC.
Signed-off-by: Mircea Caprioru <mircea.caprioru@analog.com>
Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/dac/adi,ad5770r.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2020 Analog Devices Inc.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/bindings/iio/dac/adi,ad5770r.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices AD5770R DAC device driver
+
+maintainers:
+  - Mircea Caprioru <mircea.caprioru@analog.com>
+
+description: |
+  Bindings for the Analog Devices AD5770R current DAC device. Datasheet can be
+  found here:
+    https://www.analog.com/media/en/technical-documentation/data-sheets/AD5770R.pdf
+
+properties:
+  compatible:
+    enum:
+      - adi,ad5770r
+
+  reg:
+    maxItems: 1
+
+  avdd-supply:
+    description:
+      AVdd voltage supply. Represents two different supplies in the datasheet
+      that are in fact the same.
+
+  iovdd-supply:
+    description:
+      Voltage supply for the chip interface.
+
+  vref-supply:
+    description: Specify the voltage of the external reference used.
+      Available reference options are 1.25 V or 2.5 V. If no
+      external reference declared then the device will use the
+      internal reference of 1.25 V.
+
+  adi,external-resistor:
+    description: Specify if an external 2.5k ohm resistor is used. If not
+      specified the device will use an internal 2.5k ohm resistor.
+      The precision resistor is used for reference current generation.
+    type: boolean
+
+  reset-gpios:
+    description: GPIO spec for the RESET pin. If specified, it will be
+      asserted during driver probe.
+    maxItems: 1
+
+  channel0:
+    description: Represents an external channel which are
+      connected to the DAC. Channel 0 can act both as a current
+      source and sink.
+    type: object
+
+    properties:
+      num:
+        description: This represents the channel number.
+        items:
+          const: 0
+
+      adi,range-microamp:
+          description: Output range of the channel.
+          oneOf:
+            - $ref: /schemas/types.yaml#/definitions/int32-array
+            - items:
+                - enum: [0 300000]
+                - enum: [-60000 0]
+                - enum: [-60000 300000]
+
+  channel1:
+    description: Represents an external channel which are
+      connected to the DAC.
+    type: object
+
+    properties:
+      num:
+        description: This represents the channel number.
+        items:
+          const: 1
+
+      adi,range-microamp:
+          description: Output range of the channel.
+          oneOf:
+            - $ref: /schemas/types.yaml#/definitions/uint32-array
+            - items:
+                - enum: [0 140000]
+                - enum: [0 250000]
+
+  channel2:
+    description: Represents an external channel which are
+      connected to the DAC.
+    type: object
+
+    properties:
+      num:
+        description: This represents the channel number.
+        items:
+          const: 2
+
+      adi,range-microamp:
+          description: Output range of the channel.
+          oneOf:
+            - $ref: /schemas/types.yaml#/definitions/uint32-array
+            - items:
+                - enum: [0 140000]
+                - enum: [0 250000]
+
+patternProperties:
+  "^channel@([3-5])$":
+    type: object
+    description: Represents the external channels which are connected to the DAC.
+    properties:
+      num:
+        description: This represents the channel number.
+        items:
+          minimum: 3
+          maximum: 5
+
+      adi,range-microamp:
+          description: Output range of the channel.
+          oneOf:
+            - $ref: /schemas/types.yaml#/definitions/uint32-array
+            - items:
+                - enum: [0 45000]
+                - enum: [0 100000]
+
+required:
+- reg
+- diff-channels
+- channel0
+- channel1
+- channel2
+- channel3
+- channel4
+- channel5
+
+examples:
+  - |
+        spi {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                ad5770r@0 {
+                        compatible = "ad5770r";
+                        reg = <0>;
+                        spi-max-frequency = <1000000>;
+                        vref-supply = <&vref>;
+                        adi,external-resistor;
+                        reset-gpios = <&gpio 22 0>;
+
+                        channel@0 {
+                                num = <0>;
+                                adi,range-microamp = <(-60000) 300000>;
+                        };
+
+                        channel@1 {
+                                num = <1>;
+                                adi,range-microamp = <0 140000>;
+                        };
+
+                        channel@2 {
+                                num = <2>;
+                                adi,range-microamp = <0 55000>;
+                        };
+
+                        channel@3 {
+                                num = <3>;
+                                adi,range-microamp = <0 45000>;
+                        };
+
+                        channel@4 {
+                                num = <4>;
+                                adi,range-microamp = <0 45000>;
+                        };
+
+                        channel@5 {
+                                num = <5>;
+                                adi,range-microamp = <0 45000>;
+                        };
+                };
+        };
+...