ASoC: dt-bindings: fsl_easrc: Add document for EASRC

EASRC (Enhanced Asynchronous Sample Rate Converter) is a new
IP module found on i.MX8MN.
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/3195cad960113a089d63c10e2268d63b253a69c5.1587038908.git.shengjiu.wang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

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

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/fsl,easrc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP Asynchronous Sample Rate Converter (ASRC) Controller
+
+maintainers:
+  - Shengjiu Wang <shengjiu.wang@nxp.com>
+
+properties:
+  $nodename:
+    pattern: "^easrc@.*"
+
+  compatible:
+    const: fsl,imx8mn-easrc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: Peripheral clock
+
+  clock-names:
+    items:
+      - const: mem
+
+  dmas:
+    maxItems: 8
+
+  dma-names:
+    items:
+      - const: ctx0_rx
+      - const: ctx0_tx
+      - const: ctx1_rx
+      - const: ctx1_tx
+      - const: ctx2_rx
+      - const: ctx2_tx
+      - const: ctx3_rx
+      - const: ctx3_tx
+
+  firmware-name:
+    allOf:
+      - $ref: /schemas/types.yaml#/definitions/string
+      - const: imx/easrc/easrc-imx8mn.bin
+    description: The coefficient table for the filters
+
+  fsl,asrc-rate:
+    allOf:
+      - $ref: /schemas/types.yaml#/definitions/uint32
+      - minimum: 8000
+      - maximum: 192000
+    description: Defines a mutual sample rate used by DPCM Back Ends
+
+  fsl,asrc-format:
+    allOf:
+      - $ref: /schemas/types.yaml#/definitions/uint32
+      - enum: [2, 6, 10, 32, 36]
+        default: 2
+    description:
+      Defines a mutual sample format used by DPCM Back Ends
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+  - dmas
+  - dma-names
+  - firmware-name
+  - fsl,asrc-rate
+  - fsl,asrc-format
+
+examples:
+  - |
+    #include <dt-bindings/clock/imx8mn-clock.h>
+
+    easrc: easrc@300c0000 {
+           compatible = "fsl,imx8mn-easrc";
+           reg = <0x0 0x300c0000 0x0 0x10000>;
+           interrupts = <0x0 122 0x4>;
+           clocks = <&clk IMX8MN_CLK_ASRC_ROOT>;
+           clock-names = "mem";
+           dmas = <&sdma2 16 23 0> , <&sdma2 17 23 0>,
+                  <&sdma2 18 23 0> , <&sdma2 19 23 0>,
+                  <&sdma2 20 23 0> , <&sdma2 21 23 0>,
+                  <&sdma2 22 23 0> , <&sdma2 23 23 0>;
+           dma-names = "ctx0_rx", "ctx0_tx",
+                       "ctx1_rx", "ctx1_tx",
+                       "ctx2_rx", "ctx2_tx",
+                       "ctx3_rx", "ctx3_tx";
+           firmware-name = "imx/easrc/easrc-imx8mn.bin";
+           fsl,asrc-rate  = <8000>;
+           fsl,asrc-format = <2>;
+    };