ASoC: dt-bindings: Add binding for Tegra20 S/PDIF

Add device-tree binding for Tegra20 S/PDIF controller.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20211204143725.31646-2-digetx@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/nvidia,tegra20-spdif.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/nvidia,tegra20-spdif.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NVIDIA Tegra20 S/PDIF Controller
+
+description: |
+  The S/PDIF controller supports both input and output in serial audio
+  digital interface format. The input controller can digitally recover
+  a clock from the received stream. The S/PDIF controller is also used
+  to generate the embedded audio for HDMI output channel.
+
+maintainers:
+  - Thierry Reding <treding@nvidia.com>
+  - Jon Hunter <jonathanh@nvidia.com>
+
+properties:
+  compatible:
+    const: nvidia,tegra20-spdif
+
+  reg:
+    maxItems: 1
+
+  resets:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    minItems: 2
+
+  clock-names:
+    items:
+      - const: out
+      - const: in
+
+  dmas:
+    minItems: 2
+
+  dma-names:
+    items:
+      - const: rx
+      - const: tx
+
+  "#sound-dai-cells":
+    const: 0
+
+  nvidia,fixed-parent-rate:
+    description: |
+      Specifies whether board prefers parent clock to stay at a fixed rate.
+      This allows multiple Tegra20 audio components work simultaneously by
+      limiting number of supportable audio rates.
+    type: boolean
+
+required:
+  - compatible
+  - reg
+  - resets
+  - interrupts
+  - clocks
+  - clock-names
+  - dmas
+  - dma-names
+  - "#sound-dai-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    spdif@70002400 {
+        compatible = "nvidia,tegra20-spdif";
+        reg = <0x70002400 0x200>;
+        interrupts = <77>;
+        clocks = <&clk 99>, <&clk 98>;
+        clock-names = "out", "in";
+        resets = <&rst 10>;
+        dmas = <&apbdma 3>, <&apbdma 3>;
+        dma-names = "rx", "tx";
+        #sound-dai-cells = <0>;
+    };
+
+...