ASoC: dt-bindings: Add bindings for Richtek rt9123

Document the ASoC Richtek rt9123.

Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
Link: https://patch.msgid.link/4a0b67438f82e7d8ed9968cc90acf419fc9c22cf.1744245663.git.cy_huang@richtek.com
Reviewed-by: "Rob Herring (Arm)" <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/richtek,rt9123.yaml

@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/richtek,rt9123.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Richtek RT9123 Audio Amplifier
+
+maintainers:
+  - ChiYuan Huang <cy_huang@richtek.com>
+
+description:
+  RT9123 is a 3.2W mono Class-D audio amplifier that features high efficiency
+  and performance with ultra-low quiescent current. The digital audio interface
+  support various formats, including I2S, left-justified, right-justified, and
+  TDM formats.
+
+allOf:
+  - $ref: dai-common.yaml#
+
+properties:
+  compatible:
+    enum:
+      - richtek,rt9123
+
+  reg:
+    maxItems: 1
+
+  '#sound-dai-cells':
+    const: 0
+
+  enable-gpios:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - '#sound-dai-cells'
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        amplifier@5e {
+            compatible = "richtek,rt9123";
+            reg = <0x5e>;
+            enable-gpios = <&gpio 26 GPIO_ACTIVE_HIGH>;
+            #sound-dai-cells = <0>;
+        };
+    };