ASoC: dt-bindings: Added schema for "nuvoton,nau8325"

Add a DT schema for describing nau8325 audio amplifiers. The key features
are as follows:
  - Low SPK_VDD Quiescent Current
  - Gain Setting with 2-wire interface
  - Powerful Stereo Class-D Amplifier
  - Low Output Noise
  - Low Current Shutdown Mode
  - Click-and Pop Suppression

More resources :
https://www.nuvoton.com/products/smart-home-audio/audio-amplifiers/class-d-series/nau8325yg/

Signed-off-by: Seven Lee <wtli@nuvoton.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://msgid.link/r/20240327075755.3410381-2-wtli@nuvoton.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/nuvoton,nau8325.yaml

@@ -0,0 +1,80 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/nuvoton,nau8325.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NAU8325 audio Amplifier
+
+maintainers:
+  - Seven Lee <WTLI@nuvoton.com>
+
+allOf:
+  - $ref: dai-common.yaml#
+
+properties:
+  compatible:
+    const: nuvoton,nau8325
+
+  reg:
+    maxItems: 1
+
+  nuvoton,vref-impedance-ohms:
+    description:
+      The vref impedance to be used in ohms. Middle of voltage enables
+      Tie-Off selection options. Due to the high impedance of the VREF
+      pin, it is important to use a low-leakage capacitor.
+
+    enum: [0, 25000, 125000, 2500]
+
+  nuvoton,dac-vref-microvolt:
+    description:
+      The DAC vref to be used in voltage. DAC reference voltage setting. Can
+      be used for minor tuning of the output level. Since the VDDA is range
+      between 1.62 to 1.98 voltage, the typical value for design is 1.8V. After
+      the minor tuning, the final microvolt are as the below.
+
+    enum: [1800000, 2700000, 2880000, 3060000]
+
+  nuvoton,alc-enable:
+    description:
+      Enable digital automatic level control (ALC) function.
+    type: boolean
+
+  nuvoton,clock-detection-disable:
+    description:
+      When clock detection is enabled, it will detect whether MCLK
+      and FS are within the range. MCLK range is from 2.048MHz to 24.576MHz.
+      FS range is from 8kHz to 96kHz. And also needs to detect the ratio
+      MCLK_SRC/LRCK of 256, 400 or 500, and needs to detect the BCLK
+      to make sure data is present. There needs to be at least 8 BCLK
+      cycles per Frame Sync.
+    type: boolean
+
+  nuvoton,clock-det-data:
+    description:
+      Request clock detection to require 2048 non-zero samples before enabling
+      the audio paths. If set then non-zero samples is required, otherwise it
+      doesn't matter.
+    type: boolean
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        codec@21 {
+            compatible = "nuvoton,nau8325";
+            reg = <0x21>;
+            nuvoton,vref-impedance-ohms = <125000>;
+            nuvoton,dac-vref-microvolt = <2880000>;
+            nuvoton,alc-enable;
+            nuvoton,clock-det-data;
+        };
+    };