TWL BCI (Battery Charger Interface)

Required properties:
- compatible:
  - "ti,twl4030-bci"
- interrupts: two interrupt lines from the TWL SIH (secondary
  interrupt handler) - interrupts 9 and 2.

Optional properties:
- ti,bb-uvolt: microvolts for charging the backup battery.
- ti,bb-uamp: microamps for charging the backup battery.

Examples:

bci {
   compatible = "ti,twl4030-bci";
   interrupts = <9>, <2>;
   ti,bb-uvolt = <3200000>;
   ti,bb-uamp = <150>;
};