Device tree Clock bindings for Renesas EMMA Mobile EV2

This binding uses the common clock binding.

* SMU
System Management Unit described in user's manual R19UH0037EJ1000_SMU.
This is not a clock provider, but clocks under SMU depend on it.

Required properties:
- compatible: Should be "renesas,emev2-smu"
- reg: Address and Size of SMU registers

* SMU_CLKDIV
Function block with an input mux and a divider, which corresponds to
"Serial clock generator" in fig."Clock System Overview" of the manual,
and "xxx frequency division setting register" (XXXCLKDIV) registers.
This makes internal (neither input nor output) clock that is provided
to input of xxxGCLK block.

Required properties:
- compatible: Should be "renesas,emev2-smu-clkdiv"
- reg: Byte offset from SMU base and Bit position in the register
- clocks: Parent clocks. Input clocks as described in clock-bindings.txt
- #clock-cells: Should be <0>

* SMU_GCLK
Clock gating node shown as "Clock stop processing block" in the
fig."Clock System Overview" of the manual.
Registers are "xxx clock gate control register" (XXXGCLKCTRL).

Required properties:
- compatible: Should be "renesas,emev2-smu-gclk"
- reg: Byte offset from SMU base and Bit position in the register
- clocks: Input clock as described in clock-bindings.txt
- #clock-cells: Should be <0>

Example of provider:

usia_u0_sclkdiv: usia_u0_sclkdiv {
	compatible = "renesas,emev2-smu-clkdiv";
	reg = <0x610 0>;
	clocks = <&pll3_fo>, <&pll4_fo>, <&pll1_fo>, <&osc1_fo>;
	#clock-cells = <0>;
};

usia_u0_sclk: usia_u0_sclk {
	compatible = "renesas,emev2-smu-gclk";
	reg = <0x4a0 1>;
	clocks = <&usia_u0_sclkdiv>;
	#clock-cells = <0>;
};

Example of consumer:

uart@e1020000 {
	compatible = "renesas,em-uart";
	reg = <0xe1020000 0x38>;
	interrupts = <0 8 0>;
	clocks = <&usia_u0_sclk>;
	clock-names = "sclk";
};

Example of clock-tree description:

 This describes a clock path in the clock tree
  c32ki -> pll3_fo -> usia_u0_sclkdiv -> usia_u0_sclk

smu@e0110000 {
	compatible = "renesas,emev2-smu";
	reg = <0xe0110000 0x10000>;
	#address-cells = <2>;
	#size-cells = <0>;

	c32ki: c32ki {
		compatible = "fixed-clock";
		clock-frequency = <32768>;
		#clock-cells = <0>;
	};
	pll3_fo: pll3_fo {
		compatible = "fixed-factor-clock";
		clocks = <&c32ki>;
		clock-div = <1>;
		clock-mult = <7000>;
		#clock-cells = <0>;
	};
	usia_u0_sclkdiv: usia_u0_sclkdiv {
		compatible = "renesas,emev2-smu-clkdiv";
		reg = <0x610 0>;
		clocks = <&pll3_fo>;
		#clock-cells = <0>;
	};
	usia_u0_sclk: usia_u0_sclk {
		compatible = "renesas,emev2-smu-gclk";
		reg = <0x4a0 1>;
		clocks = <&usia_u0_sclkdiv>;
		#clock-cells = <0>;
	};
};