LEGO MINDSTORMS EV3 Battery
~~~~~~~~~~~~~~~~~~~~~~~~~~~

LEGO MINDSTORMS EV3 has some built-in capability for monitoring the battery.
It uses 6 AA batteries or a special Li-ion rechargeable battery pack that is
detected by a key switch in the battery compartment.

Required properties:
 - compatible: Must be "lego,ev3-battery"
 - io-channels: phandles to analog inputs for reading voltage and current
 - io-channel-names: Must be "voltage", "current"
 - rechargeable-gpios: phandle to the rechargeable battery indication gpio

Example:

	battery {
		compatible = "lego,ev3-battery";
		io-channels = <&adc 4>, <&adc 3>;
		io-channel-names = "voltage", "current";
		rechargeable-gpios = <&gpio 136 GPIO_ACTIVE_LOW>;
	};