Synaptics SoC Device Tree Bindings

According to https://www.synaptics.com/company/news/conexant-marvell
Synaptics has acquired the Multimedia Solutions Business of Marvell, so
berlin SoCs are now Synaptics' SoCs now.

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Work in progress statement:

Device tree files and bindings applying to Marvell Berlin SoCs and boards are
considered "unstable". Any Marvell Berlin device tree binding may change at any
time. Be sure to use a device tree binary and a kernel image generated from the
same source tree.

Please refer to Documentation/devicetree/bindings/ABI.rst for a definition of a
stable binding/ABI.

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Boards with the Synaptics AS370 SoC shall have the following properties:
  Required root node property:
    compatible: "syna,as370"

Boards with a SoC of the Marvell Berlin family, e.g. Armada 1500
shall have the following properties:

* Required root node properties:
compatible: must contain "marvell,berlin"

In addition, the above compatible shall be extended with the specific
SoC and board used. Currently known SoC compatibles are:
    "marvell,berlin2"      for Marvell Armada 1500 (BG2, 88DE3100),
    "marvell,berlin2cd"    for Marvell Armada 1500-mini (BG2CD, 88DE3005)
    "marvell,berlin2ct"    for Marvell Armada ? (BG2CT, 88DE????)
    "marvell,berlin2q"     for Marvell Armada 1500-pro (BG2Q, 88DE3114)
    "marvell,berlin3"      for Marvell Armada ? (BG3, 88DE????)

* Example:

/ {
	model = "Sony NSZ-GS7";
	compatible = "sony,nsz-gs7", "marvell,berlin2", "marvell,berlin";

	...
}

* Marvell Berlin CPU control bindings

CPU control register allows various operations on CPUs, like resetting them
independently.

Required properties:
- compatible: should be "marvell,berlin-cpu-ctrl"
- reg: address and length of the register set

Example:

cpu-ctrl@f7dd0000 {
	compatible = "marvell,berlin-cpu-ctrl";
	reg = <0xf7dd0000 0x10000>;
};

* Marvell Berlin2 chip control binding

Marvell Berlin SoCs have a chip control register set providing several
individual registers dealing with pinmux, padmux, clock, reset, and secondary
CPU boot address. Unfortunately, the individual registers are spread among the
chip control registers, so there should be a single DT node only providing the
different functions which are described below.

Required properties:
- compatible:
	* the first and second values must be:
		"simple-mfd", "syscon"
- reg: address and length of following register sets for
  BG2/BG2CD: chip control register set
  BG2Q: chip control register set and cpu pll registers

* Marvell Berlin2 system control binding

Marvell Berlin SoCs have a system control register set providing several
individual registers dealing with pinmux, padmux, and reset.

Required properties:
- compatible:
	* the first and second values must be:
		"simple-mfd", "syscon"
- reg: address and length of the system control register set

Example:

chip: chip-control@ea0000 {
	compatible = "simple-mfd", "syscon";
	reg = <0xea0000 0x400>;

	/* sub-device nodes */
};

sysctrl: system-controller@d000 {
	compatible = "simple-mfd", "syscon";
	reg = <0xd000 0x100>;

	/* sub-device nodes */
};