dt-bindings: net: bluetooth: add support for MediaTek MT7663U and MT7668U UART devices

Update binding document with adding support of MT7663U and MT7668U UART
devices to mediatek-bluetooth.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

Documentation/devicetree/bindings/net/mediatek-bluetooth.txt

@@ -33,3 +33,67 @@ Example:
 			clock-names = "ref";
 		};
 	};
+
+MediaTek UART based Bluetooth Devices
+==================================
+
+This device is a serial attached device to UART device and thus it must be a
+child node of the serial node with UART.
+
+Please refer to the following documents for generic properties:
+
+	Documentation/devicetree/bindings/serial/slave-device.txt
+
+Required properties:
+
+- compatible:	Must be
+		  "mediatek,mt7663u-bluetooth": for MT7663U device
+		  "mediatek,mt7668u-bluetooth": for MT7668U device
+- vcc-supply:	Main voltage regulator
+- pinctrl-names: Should be "default", "runtime"
+- pinctrl-0: Should contain UART RXD low when the device is powered up to
+	     enter proper bootstrap mode.
+- pinctrl-1: Should contain UART mode pin ctrl
+
+Optional properties:
+
+- reset-gpios:	GPIO used to reset the device whose initial state keeps low,
+		if the GPIO is missing, then board-level design should be
+		guaranteed.
+- current-speed:  Current baud rate of the device whose defaults to 921600
+
+Example:
+
+	uart1_pins_boot: uart1-default {
+		pins-dat {
+			pinmux = <MT7623_PIN_81_URXD1_FUNC_GPIO81>;
+			output-low;
+		};
+	};
+
+	uart1_pins_runtime: uart1-runtime {
+		pins-dat {
+			pinmux = <MT7623_PIN_81_URXD1_FUNC_URXD1>,
+				 <MT7623_PIN_82_UTXD1_FUNC_UTXD1>;
+		};
+	};
+
+	uart1: serial@11003000 {
+		compatible = "mediatek,mt7623-uart",
+			     "mediatek,mt6577-uart";
+		reg = <0 0x11003000 0 0x400>;
+		interrupts = <GIC_SPI 52 IRQ_TYPE_LEVEL_LOW>;
+		clocks = <&pericfg CLK_PERI_UART1_SEL>,
+			 <&pericfg CLK_PERI_UART1>;
+		clock-names = "baud", "bus";
+
+		bluetooth {
+			compatible = "mediatek,mt7663u-bluetooth";
+			vcc-supply = <&reg_5v>;
+			reset-gpios = <&pio 24 GPIO_ACTIVE_LOW>;
+			pinctrl-names = "default", "runtime";
+			pinctrl-0 = <&uart1_pins_boot>;
+			pinctrl-1 = <&uart1_pins_runtime>;
+			current-speed = <921600>;
+		};
+	};