dt-bindings: watchdog: Convert i.MX to json-schema

Convert the i.MX watchdog 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/watchdog/fsl-imx-wdt.txt

-* Freescale i.MX Watchdog Timer (WDT) Controller
-
-Required properties:
-- compatible : Should be "fsl,<soc>-wdt"
-- reg : Should contain WDT registers location and length
-- interrupts : Should contain WDT interrupt
-
-Optional properties:
-- big-endian: If present the watchdog device's registers are implemented
-  in big endian mode, otherwise in native mode(same with CPU), for more
-  detail please see: Documentation/devicetree/bindings/regmap/regmap.txt.
-- fsl,ext-reset-output: If present the watchdog device is configured to
-  assert its external reset (WDOG_B) instead of issuing a software reset.
-- timeout-sec : Contains the watchdog timeout in seconds
-
-Examples:
-
-wdt@73f98000 {
-	compatible = "fsl,imx51-wdt", "fsl,imx21-wdt";
-	reg = <0x73f98000 0x4000>;
-	interrupts = <58>;
-	big-endian;
-	timeout-sec = <20>;
-};

Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/fsl-imx-wdt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Freescale i.MX Watchdog Timer (WDT) Controller
+
+maintainers:
+  - Anson Huang <Anson.Huang@nxp.com>
+
+allOf:
+  - $ref: "watchdog.yaml#"
+
+properties:
+  compatible:
+    enum:
+      - fsl,imx21-wdt
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  fsl,ext-reset-output:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description: |
+      If present, the watchdog device is configured to assert its
+      external reset (WDOG_B) instead of issuing a software reset.
+
+required:
+  - compatible
+  - interrupts
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/imx6qdl-clock.h>
+
+    watchdog@20bc000 {
+        compatible = "fsl,imx21-wdt";
+        reg = <0x020bc000 0x4000>;
+        interrupts = <0 80 IRQ_TYPE_LEVEL_HIGH>;
+        clocks = <&clks IMX6QDL_CLK_IPG>;
+    };
+
+...