Add devicetree bindings for Rockchip cru which found on
Rockchip SoCs.

Signed-off-by: Elaine Zhang <redacted>
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 .../bindings/clock/rockchip,rk3328-cru.txt         | 57
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Documentation/devicetree/bindings/clock/rockchip,rk3328-cru.txt

diff --git a/Documentation/devicetree/bindings/clock/rockchip,rk3328-cru.txt

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+* Rockchip RK3328 Clock and Reset Unit
+
+The RK3328 clock controller generates and supplies clock to various
+controllers within the SoC and also implements a reset controller for SoC
+peripherals.
+
+Required Properties:
+
+- compatible: should be "rockchip,rk3328-cru"
+- reg: physical base address of the controller and length of memory mapped
+  region.
+- #clock-cells: should be 1.
+- #reset-cells: should be 1.
+
+Optional Properties:
+
+- rockchip,grf: phandle to the syscon managing the "general register files"
+  If missing pll rates are not changeable, due to the missing pll lock

status. +
+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/rk3328-cru.h
headers and can be +used in device tree sources. Similar macros exist for
the reset sources in +these files.
+
+External clocks:
+
+There are several clocks that are generated outside the SoC. It is expected
+that they are defined using standard clock bindings with following
+clock-output-names:
+ - "xin24m" - crystal input - required,
+ - "clkin_i2s" - external I2S clock - optional,
+ - "gmac_clkin" - external GMAC clock - optional
+ - "phy_50m_out" - output clock of the pll in the mac phy
+
+Example: Clock controller node:
+
+	cru: clock-controller@ff440000 {
+		compatible = "rockchip,rk3328-cru", "rockchip,cru", "syscon";