* Rockchip RK3288 Clock and Reset Unit

The RK3288 clock controller generates and supplies clock to various
controllers within the SoC and also implements a reset controller for SoC
peripherals.

A revision of this SoC is available: rk3288w. The clock tree is a bit
different so another dt-compatible is available. Noticed that it is only
setting the difference but there is no automatic revision detection. This
should be performed by bootloaders.

Required Properties:

- compatible: should be "rockchip,rk3288-cru" or "rockchip,rk3288w-cru" in
  case of this revision of Rockchip rk3288.
- 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/rk3288-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,
 - "xin32k" - rtc clock - optional,
 - "ext_i2s" - external I2S clock - optional,
 - "ext_hsadc" - external HSADC clock - optional,
 - "ext_edp_24m" - external display port clock - optional,
 - "ext_vip" - external VIP clock - optional,
 - "ext_isp" - external ISP clock - optional,
 - "ext_jtag" - external JTAG clock - optional

Example: Clock controller node:

	cru: cru@20000000 {
		compatible = "rockchip,rk3188-cru";
		reg = <0x20000000 0x1000>;
		rockchip,grf = <&grf>;

		#clock-cells = <1>;
		#reset-cells = <1>;
	};

Example: UART controller node that consumes the clock generated by the clock
  controller:

	uart0: serial@10124000 {
		compatible = "snps,dw-apb-uart";
		reg = <0x10124000 0x400>;
		interrupts = <GIC_SPI 34 IRQ_TYPE_LEVEL_HIGH>;
		reg-shift = <2>;
		reg-io-width = <1>;
		clocks = <&cru SCLK_UART0>;
	};