ASoC: dt-bindings: codecs: Add bindings for ak4375

AK4375 is an audio DAC with headphones amplifier controlled via I2C.
Add simple device tree bindings that describe how to set it up.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vincent Knecht <vincent.knecht@mailoo.org>
Link: https://lore.kernel.org/r/20211220193725.2650356-1-vincent.knecht@mailoo.orgSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/ak4375.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/ak4375.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: AK4375 DAC and headphones amplifier Device Tree Bindings
+
+maintainers:
+  - Vincent Knecht <vincent.knecht@mailoo.org>
+
+properties:
+  compatible:
+    const: asahi-kasei,ak4375
+
+  reg:
+    maxItems: 1
+
+  '#sound-dai-cells':
+    const: 0
+
+  avdd-supply:
+    description: regulator phandle for the AVDD power supply.
+
+  tvdd-supply:
+    description: regulator phandle for the TVDD power supply.
+
+  pdn-gpios:
+    description: optional GPIO to set the PDN pin.
+
+required:
+  - compatible
+  - reg
+  - '#sound-dai-cells'
+  - avdd-supply
+  - tvdd-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      headphones: audio-codec@10 {
+        compatible = "asahi-kasei,ak4375";
+        reg = <0x10>;
+        avdd-supply = <&reg_headphones_avdd>;
+        tvdd-supply = <&pm8916_l6>;
+        pdn-gpios = <&msmgpio 114 GPIO_ACTIVE_HIGH>;
+        pinctrl-names = "default";
+        pinctrl-0 = <&headphones_pdn_default>;
+        #sound-dai-cells = <0>;
+      };
+    };