dt-binding: clock: Document rockchip, rk3568-cru bindings

Document the device tree bindings of the rockchip Rk3568 SoC
clock driver in Documentation/devicetree/bindings/clock/rockchip,rk3568-cru.yaml.
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20210315085608.16010-2-zhangqing@rock-chips.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/clock/rockchip,rk3568-cru.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/rockchip,rk3568-cru.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ROCKCHIP rk3568 Family Clock Control Module Binding
+
+maintainers:
+  - Elaine Zhang <zhangqing@rock-chips.com>
+  - Heiko Stuebner <heiko@sntech.de>
+
+description: |
+  The RK3568 clock controller generates the clock and also implements a
+  reset controller for SoC peripherals.
+  (examples: provide SCLK_UART1\PCLK_UART1 and SRST_P_UART1\SRST_S_UART1 for UART module)
+  Each clock is assigned an identifier and client nodes can use this identifier
+  to specify the clock which they consume. All available clocks are defined as
+  preprocessor macros in the dt-bindings/clock/rk3568-cru.h headers and can be
+  used in device tree sources.
+
+properties:
+  compatible:
+    enum:
+      - rockchip,rk3568-cru
+      - rockchip,rk3568-pmucru
+
+  reg:
+    maxItems: 1
+
+  "#clock-cells":
+    const: 1
+
+  "#reset-cells":
+    const: 1
+
+required:
+  - compatible
+  - reg
+  - "#clock-cells"
+  - "#reset-cells"
+
+additionalProperties: false
+
+examples:
+  # Clock Control Module node:
+  - |
+    pmucru: clock-controller@fdd00000 {
+      compatible = "rockchip,rk3568-pmucru";
+      reg = <0xfdd00000 0x1000>;
+      #clock-cells = <1>;
+      #reset-cells = <1>;
+    };
+  - |
+    cru: clock-controller@fdd20000 {
+      compatible = "rockchip,rk3568-cru";
+      reg = <0xfdd20000 0x1000>;
+      #clock-cells = <1>;
+      #reset-cells = <1>;
+    };