DT binding document for INA3221 iio/meter driver.

Required properties:
- compatible: Must be "ti,ina3221x".
- reg: I2C slave address of device.

- ti,trigger-config: Trigger configuration for the device in trigger mode.
- ti,continuous-config:  Device configuration in continuous mode. In this mode
	device will keep scanning the inputs.
- address-cells: Number of address in child node. Must be 1.
- size-cells: Size of address cell. Must be 0.

Optional sub-nodes:
	Device has 3 input channels and channel specific information
is provided through the child node. Each channel will have different child
node. The channel number is identified by the reg properties on each of node.
Required subnode properties:
- reg: channel number. 0 for channel 0, 1 for channel 1 and 2 for channel 2.
- ti,rail-mae: Name of the channel in string.

Optional subnode properties:
- ti,current-warning-limit-ma: Cureent warning limit for the given channel.
- ti,current-critical-limit-ma: Current critical limit for the given channel.
- ti,shunt-resistor-mohm: Shunt register in milli ohm.

IIO channel properties:
It follows same mechanism for iio properties detailed on ../iio-bindings.txt
The iio cells size must be 1.
	#io-channel-cells = <1>;
The ina3221 driver provides following monitoring:
	voltage, current, current_trigger, power, power_trigger.
	The sequence of index assigned in drivers are:
		voltage, current, current_trigger, power, power_trigger
	The above monitoring is provided for channel 0, 1 and 2.
The sysfs are
	in_voltage0_input, in_current0_input, in_current0_trigger_input
	in_power0_input, in_power0_trigger_input
	in_voltage1_input, in_current1_input, in_current1_trigger_input,
	in_power1_input, in_power1_trigger_input
	in_voltage2_input, in_current2_input, in_current2_trigger_input,
	in_power2_input,in_power2_trigger_input
The channel index are in above sequence starting from 0.

To ease the DT entry, the macros are added in header dt-bindings/iio/meter/ina3221x.h
The Voltage/current/power macros are defines and can be use with INA3221_CHAN_INDEX to
get the proper index.
Example: For Channel 0, normal power it is INA3221_CHAN_INDEX(0, POWER, NORMAL)
for channel 2, normal current it is INA3221_CHAN_INDEX(2, CURRENT, NORMAL).

The typical macro for voltage/current and powers are:
	INA3221_VOLTAGE, INA3221_CURRENT, INA3221_POWER
The typical macro for normal/trigger are INA3221_NORMAL and INA3221_TRIGGER.

The INA3221_CHAN_INDEX defined as:
#define INA3221_CHAN_INDEX(chan, type, add) (chan * 5 + INA3221_##type + INA3221_##add)

Example:
	ina3221x@40 {
		compatible = "ti,ina3221x";
		reg = <0x40>;
		ti,trigger-config = <0x7003>;
		ti,continuous-config = <0x7c07>;
		#address-cells = <1>;
		#size-cells = <0>;
		#io-channel-cells = <1>;

		channel@0 {
			reg = <0x0>;
			ti,rail-name = "VDD_BAT";
			ti,current-warning-limit-ma = <8000>;
			ti,current-critical-limit-ma = <9000>;
			ti,shunt-resistor-mohm = <1>;
		};

		channel@1 {
			reg = <0x1>;
			ti,rail-name = "VDD_CPU";
			ti,shunt-resistor-mohm = <1>;
		};

		channel@2 {
			reg = <0x2>;
			ti,rail-name = "VDD_GPU";
			ti,shunt-resistor-mohm = <1>;
		};
	};


clients {
	io-channels = <&ina3221x INA3221_CHAN_INDEX(0, CURRENT, NORMAL)>;
	io-channel-names = "battery-current"
}
