Marvell Thermal Sensor binding
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The thermal node includes a description of the Thermal Sensor External Unit.
The thernal sensor is an on-chip temperature sensor that reads the temperature of
every core and returns the average or the maximum between them.

Mandatory properties:
SoC specific:
	- compatible: should contain two compatibles:
		- first: "marvell,mvebu-thermal"
		- second: indicate the thermal sensor type
		"marvell,thermal-sensor" or "marvell,thermal-ext-sensor"
	- reg: the base address of thermal unit
	- gain, offset: parameters of the temperature equation
		which are:
		T(in Celsius) = T(read value) * gain + offset

	- divisor: the value that multiply with gain and offset; see Note.
		Note: in the Tsen spec the default value of gain equals 0.425
		In the u-boot we cannot calculate a real number (no floating point).
		For this reason, set the gain and offset by multiplying them by divisor
		value (usually 1000 or 10000).
		This helps to calculate the equation; see example below.


- In Armada80x0/70x0 there are 2 types of thermal sensor:
	- regular sensor (integrated in CP)
	- external sensor (integrated in AP)

Example for external sensor (integrated in AP):

The required calculation:
T(in Celsius) = T(read value) * 0.425 + 153.4
The calculation in u-boot:
T(in Celsius) = (T(read value) * 425 + 153400) / 1000

Example:
	thermal: thermal@6f8084 {
		compatible = "marvell,mvebu-thermal", "marvell,thermal-ext-sensor";
		reg = <0x6f8084 0x12>;
		gain = <425>;
		offset = <153400>;
		divisor = <1000>;
		status = "okay";
	};

Example for regular sensor (integrated in CP):

The required calculation:
T(in Celsius) = T(read value) * 0.4761 - 279.1
The calculation in u-boot:
T(in Celsius) = (T(read value) * 4761 - 2791000) / 10000

Example:
	thermal@400070 {
		compatible = "marvell,mvebu-thermal", "marvell,thermal-sensor";
		reg = <0x400070 0x12>;
		gain = <4761>;
		offset = <2791000>;
		divisor = <10000>;
		status = "okay";
	};
