ASoC: dt-bindings: Add Realtek ALC203 Codec

Add devicetree binding document for Realtek ALC203 codec.

Signed-off-by: Keguang Zhang <keguang.zhang@gmail.com>
Link: https://patch.msgid.link/20250409-loongson1-ac97-v2-2-65d5db96a046@gmail.com
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/realtek,alc203.yaml

@@ -0,0 +1,36 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/realtek,alc203.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek ALC203 AC97 Audio Codec
+
+maintainers:
+  - Keguang Zhang <keguang.zhang@gmail.com>
+
+description:
+  ALC203 is a full duplex AC97 2.3 compatible stereo audio codec.
+
+allOf:
+  - $ref: dai-common.yaml#
+
+properties:
+  compatible:
+    const: realtek,alc203
+
+  '#sound-dai-cells':
+    const: 0
+
+required:
+  - compatible
+  - '#sound-dai-cells'
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    audio-codec {
+        compatible = "realtek,alc203";
+        #sound-dai-cells = <0>;
+    };