dt-bindings: watchdog: Convert UniPhier watchdog timer to json-schema

Convert UniPhier watchdog timer binding to DT schema format.

Cc: Keiji Hayashibara <hayashibara.keiji@socionext.com>
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/watchdog/socionext,uniphier-wdt.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/socionext,uniphier-wdt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Socionext UniPhier watchdog timer
+
+maintainers:
+  - Keiji Hayashibara <hayashibara.keiji@socionext.com>
+
+allOf:
+  - $ref: "watchdog.yaml#"
+
+properties:
+  compatible:
+    const: socionext,uniphier-wdt
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    // The UniPhier watchdog should be a subnode of a "syscon" compatible node.
+
+    sysctrl@61840000 {
+        compatible = "socionext,uniphier-ld11-sysctrl",
+                     "simple-mfd", "syscon";
+        reg = <0x61840000 0x10000>;
+
+        watchdog {
+            compatible = "socionext,uniphier-wdt";
+        };
+    };

Documentation/devicetree/bindings/watchdog/uniphier-wdt.txt

-UniPhier watchdog timer controller
-
-This UniPhier watchdog timer controller must be under sysctrl node.
-
-Required properties:
-- compatible: should be "socionext,uniphier-wdt"
-
-Example:
-
-	sysctrl@61840000 {
-		compatible = "socionext,uniphier-ld11-sysctrl",
-			     "simple-mfd", "syscon";
-		reg = <0x61840000 0x4000>;
-
-		watchdog {
-			compatible = "socionext,uniphier-wdt";
-		}
-
-		other nodes ...
-	};