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

Convert the mxs pwm binding to DT schema format using json-schema.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Rob Herring <robh@kernel.org>

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

-Freescale MXS PWM controller
-
-Required properties:
-- compatible: should be "fsl,imx23-pwm"
-- reg: physical base address and length of the controller's registers
-- #pwm-cells: should be 3. See pwm.yaml in this directory for a description of
-  the cells format.
-- fsl,pwm-number: the number of PWM devices
-
-Example:
-
-pwm: pwm@80064000 {
-	compatible = "fsl,imx28-pwm", "fsl,imx23-pwm";
-	reg = <0x80064000 0x2000>;
-	#pwm-cells = <3>;
-	fsl,pwm-number = <8>;
-};

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

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/mxs-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Freescale MXS PWM controller
+
+maintainers:
+  - Shawn Guo <shawn.guo@linaro.org>
+  - Anson Huang <anson.huang@nxp.com>
+
+properties:
+  compatible:
+    enum:
+      - fsl,imx23-pwm
+
+  reg:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 3
+
+  fsl,pwm-number:
+    $ref: '/schemas/types.yaml#/definitions/uint32'
+    description: u32 value representing the number of PWM devices
+
+required:
+  - compatible
+  - reg
+  - "#pwm-cells"
+  - fsl,pwm-number
+
+additionalProperties: false
+
+examples:
+  - |
+    pwm@80064000 {
+        compatible = "fsl,imx23-pwm";
+        reg = <0x80064000 0x2000>;
+        #pwm-cells = <3>;
+        fsl,pwm-number = <8>;
+    };