* Allwinner P2WI (Push/Pull 2 Wire Interface) controller

Required properties :

 - reg             : Offset and length of the register set for the device.
 - compatible      : Should one of the following:
                     - "allwinner,sun6i-a31-p2wi"
 - interrupts      : The interrupt line connected to the P2WI peripheral.
 - clocks          : The gate clk connected to the P2WI peripheral.
 - resets          : The reset line connected to the P2WI peripheral.

Optional properties :

 - clock-frequency : Desired P2WI bus clock frequency in Hz. If not set the
default frequency is 100kHz

A P2WI may contain one child node encoding a P2WI slave device.

Slave device properties:
  Required properties:
   - reg           : the I2C slave address used during the initialization
                     process to switch from I2C to P2WI mode

Example:

	p2wi@1f03400 {
		compatible = "allwinner,sun6i-a31-p2wi";
		reg = <0x01f03400 0x400>;
		interrupts = <0 39 4>;
		clocks = <&apb0_gates 3>;
		clock-frequency = <6000000>;
		resets = <&apb0_rst 3>;

		axp221: pmic@68 {
			compatible = "x-powers,axp221";
			reg = <0x68>;

			/* ... */
		};
	};