ASoC: dt-bindings: fsl_aud2htx: Add binding doc for aud2htx module

AUD2HTX (Audio Subsystem TO HDMI TX Subsystem) is a new
IP module found on i.MX8MP.
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1604281947-26874-1-git-send-email-shengjiu.wang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/fsl,aud2htx.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/fsl,aud2htx.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP Audio Subsystem to HDMI RTX Subsystem Controller
+
+maintainers:
+  - Shengjiu Wang <shengjiu.wang@nxp.com>
+
+properties:
+  compatible:
+    const: fsl,imx8mp-aud2htx
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: Peripheral clock
+
+  clock-names:
+    items:
+      - const: bus
+
+  dmas:
+    items:
+      - description: DMA controller phandle and request line for TX
+
+  dma-names:
+    items:
+      - const: tx
+
+  power-domains:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+  - dmas
+  - dma-names
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/imx8mp-clock.h>
+
+    aud2htx: aud2htx@30cb0000 {
+        compatible = "fsl,imx8mp-aud2htx";
+        reg = <0x30cb0000 0x10000>;
+        interrupts = <GIC_SPI 130 IRQ_TYPE_LEVEL_HIGH>;
+        clocks = <&audiomix_clk IMX8MP_CLK_AUDIOMIX_AUD2HTX_IPG>;
+        clock-names = "bus";
+        dmas = <&sdma2 26 2 0>;
+        dma-names = "tx";
+        power-domains = <&audiomix_pd>;
+    };