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 <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Stephen Boyd <[e-mail]>

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

···
+# 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 <[e-mail]>
+
+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>;
+    };
+
+...

include/dt-bindings/clock/loongson,ls1x-clk.h

···
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
+/*
+ * Loongson-1 clock tree IDs
+ *
+ * Copyright (C) 2023 Keguang Zhang <[e-mail]>
+ */
+
+#ifndef __DT_BINDINGS_CLOCK_LS1X_CLK_H__
+#define __DT_BINDINGS_CLOCK_LS1X_CLK_H__
+
+#define LS1X_CLKID_PLL	0
+#define LS1X_CLKID_CPU	1
+#define LS1X_CLKID_DC	2
+#define LS1X_CLKID_AHB	3
+#define LS1X_CLKID_APB	4
+
+#define CLK_NR_CLKS	(LS1X_CLKID_APB + 1)
+
+#endif /* __DT_BINDINGS_CLOCK_LS1X_CLK_H__ */