Sandbox pmic

This device uses two drivers:
- drivers/power/pmic/sandbox.c (for parent device)
- drivers/power/regulator/sandbox.c (for child regulators)

This file describes the binding info for the PMIC driver.

To bind the regulators, please read the regulator binding info:
- doc/device-tree-bindings/regulator/sandbox.txt

Required PMIC node properties:
- compatible: "sandbox,pmic"
- reg = 0x40

Required PMIC's "emul" subnode,  with property:
- compatible: "sandbox,i2c-pmic"

With the above properties, the pmic device can be used for read/write only.
To bind each regulator, the optional regulator subnodes should exists.

Optional subnodes:
- ldo/buck subnodes of each device's regulator (see regulator binding info)

Example:

sandbox_pmic {
	compatible = "sandbox,pmic";
	reg = <0x40>;

	/* Mandatory for I/O */
	emul {
		compatible = "sandbox,i2c-pmic";
	};
};