overlays: Add overlay for QCA7000 via UART0

This adds an overlay to connect the QCA7000 in UART mode via UART0.
The qcauart driver uses the serial device bus instead of deprecated
line disciplines.

Signed-off-by: Stefan Wahren <stefan.wahren@in-tech.com>

arch/arm/boot/dts/overlays/Makefile

@@ -157,6 +157,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	pwm-2chan.dtbo \
 	pwm-ir-tx.dtbo \
 	qca7000.dtbo \
+	qca7000-uart0.dtbo \
 	rotary-encoder.dtbo \
 	rpi-backlight.dtbo \
 	rpi-cirrus-wm5102.dtbo \

arch/arm/boot/dts/overlays/README

@@ -2505,12 +2505,23 @@ Params: gpio_pin                Output GPIO (default 18)
 
 Name:   qca7000
 Info:   in-tech's Evaluation Board for PLC Stamp micro
+        This uses spi0 and a separate GPIO interrupt to connect the QCA7000.
 Load:   dtoverlay=qca7000,<param>=<val>
 Params: int_pin                 GPIO pin for interrupt signal (default 23)
 
         speed                   SPI bus speed (default 12 MHz)
 
 
+Name:   qca7000-uart0
+Info:   in-tech's Evaluation Board for PLC Stamp micro (UART)
+        This uses uart0/ttyAMA0 over GPIOs 14 & 15 to connect the QCA7000.
+        But it requires disabling of onboard Bluetooth on
+        Pi 3B, 3B+, 3A+, 4B and Zero W.
+Load:   dtoverlay=qca7000-uart0,<param>=<val>
+Params: baudrate                Set the baudrate for the UART (default
+                                "115200")
+
+
 Name:   rotary-encoder
 Info:   Overlay for GPIO connected rotary encoder.
 Load:   dtoverlay=rotary-encoder,<param>=<val>

arch/arm/boot/dts/overlays/qca7000-uart0-overlay.dts

@@ -0,0 +1,46 @@
+// Overlay for the Qualcomm Atheros QCA7000 on PLC Stamp micro EVK
+// Visit: https://in-tech-smartcharging.com/products/evaluation-tools/plc-stamp-micro-2-evaluation-board for details
+
+/dts-v1/;
+/plugin/;
+
+/ {
+	compatible = "brcm,bcm2835";
+
+	fragment@0 {
+		target = <&uart0>;
+		__overlay__ {
+			pinctrl-names = "default";
+			pinctrl-0 = <&uart0_pins>;
+			status = "okay";
+
+			eth2: qca7000 {
+				compatible = "qca,qca7000";
+				current-speed = <115200>;
+			};
+		};
+	};
+
+	fragment@1 {
+		target = <&gpio>;
+		__overlay__ {
+			uart0_pins: uart0_pins {
+				brcm,pins = <14 15>;
+				brcm,function = <4>; /* alt0 */
+				brcm,pull = <0 2>;
+			};
+		};
+	};
+
+	fragment@2 {
+		target-path = "/aliases";
+		__overlay__ {
+			serial0 = "/soc/serial@7e201000";
+			serial1 = "/soc/serial@7e215040";
+		};
+	};
+
+	__overrides__ {
+		baudrate = <&eth2>, "current-speed:0";
+	};
+};