* Bluetooth Controller
Bluetooth controller communicates with the Bluetooth Host using HCI Transport
layer. HCI Transport layer can be based on UART or USB serial communication
protocol.

Required properties:
	- compatible: Should be set to one of the following:
		qca,ar3002
		qca,qca6174
		qca,qca6390
		qca,wcn3990
	- qca,bt-reset-gpio: GPIO pin to bring BT Controller out of reset

Optional properties:
	- qca,bt-vdd-pa-supply: Bluetooth VDD PA regulator handle
	- qca,bt-vdd-io-supply: Bluetooth VDD IO regulator handle
	- qca,bt-vdd-ldo-supply: Bluetooth VDD LDO regulator handle. Kept under
		optional parameters as some of the chipsets doesn't require ldo
		or it may use from same vddio.
	- qca,bt-vdd-xtal-supply: Bluetooth VDD XTAL regulator handle
	- qca,bt-vdd-core-supply: Bluetooth VDD CORE regulator handle
	- qca,bt-chip-pwd-supply: Chip power down gpio is required when bluetooth
		module and other modules like wifi co-exist in a singe chip and
		shares a common gpio to bring chip out of reset.
	- qca,bt-vdd-pa-voltage-level: specifies VDD PA voltage levels for supply.
		Should be specified in pairs (min, max), units uV
	- qca,bt-vdd-io-voltage-level: specifies VDD IO voltage levels for supply.
		Should be specified in pairs (min, max), units uV
	- qca,bt-vdd-ldo-voltage-level: specifies VDD LDO voltage levels for supply.
		Should be specified in pairs (min, max), units uV
	- qca,bt-vdd-xtal-voltage-level: specifies VDD XTAL voltage levels for supply.
		Should be specified in pairs (min, max), units uV
	- qca,bt-vdd-core-voltage-level: specifies VDD CORE voltage levels for supply.
		Should be specified in pairs (min, max), units uV
	- qca,bt-vdd-io-current-level: specifies VDD IO current level in microamps
	- qca,bt-vdd-xtal-current-level: specifies VDD XTAL current level in microamps
	- qca,bt-vdd-core-current-level: specifies VDD CORE current level in microamps.
	- qca,bt-vdd-ldo-current-level: specifies VDD LDO current level in microamps.
	- qca,bt-vdd-pa-current-level: specifies VDD PA current level in microamps.
	- qca,bt-chip-pwd-current-level: specifies Chip Power current level in microamps.

Example:
	bt-ar3002 {
		compatible = "qca,ar3002";
		qca,bt-reset-gpio = <&pm8941_gpios 34 0>;
		qca,bt-vdd-io-supply = <&pm8941_s3>;
		qca,bt-vdd-pa-supply = <&pm8941_l19>;
		qca,bt-vdd-xtal-supply = <&pm8994_l30>;
		qca,bt-vdd-core-supply = <&pm8994_s3>;
		qca,bt-chip-pwd-supply = <&ath_chip_pwd_l>;

		qca,bt-vdd-io-voltage-level = <1800000 1800000>;
		qca,bt-vdd-pa-voltage-level = <2900000 2900000>;
		qca,bt-vdd-xtal-voltage-level = <1800000 1800000>;
		qca,bt-vdd-core-voltage-level = <1300000 1300000>;

		qca,bt-vdd-io-current-level = <1>; /* LPM/PFM */
		qca,bt-vdd-xtal-current-level = <1>; /* LPM/PFM */
		qca,bt-vdd-core-current-level = <1>; /* LPM/PFM */
		qca,bt-vdd-ldo-current-level = <1>; /* LPM/PFM */
		qca,bt-vdd-pa-current-level = <1>; /* LPM/PFM */
	};
