dt-bindings: mips: Add Loongson-2K1000 reset support

Switch the DT binding to a YAML schema to enable the DT validation.
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Documentation/devicetree/bindings/mips/loongson/ls2k-reset.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/mips/loongson/ls2k-reset.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Loongson 2K1000 PM Controller
+
+maintainers:
+  - Qing Zhang <zhangqing@loongson.cn>
+
+description: |
+  This controller can be found in Loongson-2K1000 Soc systems.
+
+properties:
+  compatible:
+    const: loongson,ls2k-pm
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    bus {
+        #address-cells = <2>;
+        #size-cells = <2>;
+        pm: reset-controller@1fe07000 {
+            compatible = "loongson,ls2k-pm";
+            reg = <0 0x1fe07000 0 0x422>;
+        };
+    };
+...