* 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,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

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>;
  };