ASoC: adau1372: Add bindings documentation

Add device tree binding documentation for Analog Devices ADAU1372.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201127123030.1610574-1-alexandre.belloni@bootlin.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/adi,adau1372.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/adi,adau1372.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+
+title: Analog Devices ADAU1372 CODEC
+
+maintainers:
+  - Alexandre Belloni <alexandre.belloni@bootlin.om>
+
+description: |
+  Analog Devices ADAU1372 four inputs and two outputs codec.
+  https://www.analog.com/media/en/technical-documentation/data-sheets/ADAU1372.pdf
+
+properties:
+  compatible:
+    enum:
+      - adi,adau1372
+
+  reg:
+    maxItems: 1
+
+  "#sound-dai-cells":
+    const: 0
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    const: "mclk"
+
+  powerdown-gpios:
+    description: GPIO used for hardware power-down.
+    maxItems: 1
+
+required:
+  - "#sound-dai-cells"
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        audio-codec@3c {
+                compatible = "adi,adau1372";
+                reg = <0x3c>;
+                #sound-dai-cells = <0>;
+                clock-names = "mclk";
+                clocks = <&adau1372z_xtal>;
+        };
+    };
+
+    adau1372z_xtal: clock {
+        compatible = "fixed-clock";
+        #clock-cells = <0>;
+        clock-frequency = <12288000>;
+    };
+...
+