dt-bindings: spi: Convert mxs spi to json-schema

Convert the MXS SPI binding to DT schema format using json-schema
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1592281575-32708-2-git-send-email-Anson.Huang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/mxs-spi.txt

-* Freescale MX233/MX28 SSP/SPI
-
-Required properties:
-- compatible: Should be "fsl,<soc>-spi", where soc is "imx23" or "imx28"
-- reg: Offset and length of the register set for the device
-- interrupts: Should contain SSP ERROR interrupt
-- dmas: DMA specifier, consisting of a phandle to DMA controller node
-  and SSP DMA channel ID.
-  Refer to dma.txt and fsl-mxs-dma.txt for details.
-- dma-names: Must be "rx-tx".
-
-Optional properties:
-- clock-frequency : Input clock frequency to the SPI block in Hz.
-		    Default is 160000000 Hz.
-
-Example:
-
-ssp0: ssp@80010000 {
-	#address-cells = <1>;
-	#size-cells = <0>;
-	compatible = "fsl,imx28-spi";
-	reg = <0x80010000 0x2000>;
-	interrupts = <96>;
-	dmas = <&dma_apbh 0>;
-	dma-names = "rx-tx";
-};

Documentation/devicetree/bindings/spi/mxs-spi.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/spi/mxs-spi.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Freescale MX233/MX28 SSP/SPI
+
+maintainers:
+  - Marek Vasut <marex@denx.de>
+
+allOf:
+  - $ref: "/schemas/spi/spi-controller.yaml#"
+
+properties:
+  compatible:
+    enum:
+      - fsl,imx23-spi
+      - fsl,imx28-spi
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  dmas:
+    maxItems: 1
+
+  dma-names:
+    const: rx-tx
+
+  clock-frequency:
+    description: input clock frequency to the SPI block in Hz.
+    default: 160000000
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - dmas
+  - dma-names
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    spi@80010000 {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        compatible = "fsl,imx28-spi";
+        reg = <0x80010000 0x2000>;
+        interrupts = <96>;
+        dmas = <&dma_apbh 0>;
+        dma-names = "rx-tx";
+    };