ASoC: dt-bindings: Add Rockchip RK3308 internal audio codec

Add device tree bindings document for the internal audio codec of the
Rockchip RK3308 SoC.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://msgid.link/r/20240305-rk3308-audio-codec-v4-2-312acdbe628f@bootlin.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/rockchip,rk3308-codec.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/rockchip,rk3308-codec.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Rockchip RK3308 Internal Codec
+
+description: |
+  This is the audio codec embedded in the Rockchip RK3308
+  SoC. It has 8 24-bit ADCs and 2 24-bit DACs. The maximum supported
+  sampling rate is 192 kHz.
+
+  It is connected internally to one out of a selection of the internal I2S
+  controllers.
+
+  The RK3308 audio codec has 8 independent capture channels, but some
+  features work on stereo pairs called groups:
+    * grp 0 -- MIC1 / MIC2
+    * grp 1 -- MIC3 / MIC4
+    * grp 2 -- MIC5 / MIC6
+    * grp 3 -- MIC7 / MIC8
+
+maintainers:
+  - Luca Ceresoli <luca.ceresoli@bootlin.com>
+
+properties:
+  compatible:
+    const: rockchip,rk3308-codec
+
+  reg:
+    maxItems: 1
+
+  rockchip,grf:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Phandle to the General Register Files (GRF)
+
+  clocks:
+    items:
+      - description: clock for TX
+      - description: clock for RX
+      - description: AHB clock driving the interface
+
+  clock-names:
+    items:
+      - const: mclk_tx
+      - const: mclk_rx
+      - const: hclk
+
+  resets:
+    maxItems: 1
+
+  reset-names:
+    items:
+      - const: codec
+
+  "#sound-dai-cells":
+    const: 0
+
+  rockchip,micbias-avdd-percent:
+    description: |
+      Voltage setting for the MICBIAS pins expressed as a percentage of
+      AVDD.
+
+      E.g. if rockchip,micbias-avdd-percent = 85 and AVDD = 3v3, then the
+      MIC BIAS voltage will be 3.3 V * 85% = 2.805 V.
+
+    enum: [ 50, 55, 60, 65, 70, 75, 80, 85 ]
+
+required:
+  - compatible
+  - reg
+  - rockchip,grf
+  - clocks
+  - resets
+  - "#sound-dai-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/rk3308-cru.h>
+
+    audio_codec: audio-codec@ff560000 {
+        compatible = "rockchip,rk3308-codec";
+        reg = <0xff560000 0x10000>;
+        rockchip,grf = <&grf>;
+        clock-names = "mclk_tx", "mclk_rx", "hclk";
+        clocks = <&cru SCLK_I2S2_8CH_TX_OUT>,
+                 <&cru SCLK_I2S2_8CH_RX_OUT>,
+                 <&cru PCLK_ACODEC>;
+        reset-names = "codec";
+        resets = <&cru SRST_ACODEC_P>;
+        #sound-dai-cells = <0>;
+    };
+
+...

MAINTAINERS

@@ -19046,6 +19046,11 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/media/rockchip-rga.yaml
 F:	drivers/media/platform/rockchip/rga/
 
+ROCKCHIP RK3308 INTERNAL AUDIO CODEC
+M:	Luca Ceresoli <luca.ceresoli@bootlin.com>
+S:	Maintained
+F:	Documentation/devicetree/bindings/sound/rockchip,rk3308-codec.yaml
+
 ROCKCHIP VIDEO DECODER DRIVER
 M:	Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
 L:	linux-media@vger.kernel.org