dt-bindings: clock: Add Loongson-1 clock

Add devicetree binding document and related header file
for the Loongson-1 clock.

Signed-off-by: Keguang Zhang <keguang.zhang@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230321111817.71756-2-keguang.zhang@gmail.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/loongson,ls1x-clk.yaml

@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/loongson,ls1x-clk.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Loongson-1 Clock Controller
+
+maintainers:
+  - Keguang Zhang <keguang.zhang@gmail.com>
+
+properties:
+  compatible:
+    enum:
+      - loongson,ls1b-clk
+      - loongson,ls1c-clk
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  "#clock-cells":
+    const: 1
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - "#clock-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    clkc: clock-controller@1fe78030 {
+        compatible = "loongson,ls1b-clk";
+        reg = <0x1fe78030 0x8>;
+
+        clocks = <&xtal>;
+        #clock-cells = <1>;
+    };
+
+...