ath79: add support for onion omega

The Onion Omega is a hardware development platform with built-in WiFi.

https://onioniot.github.io/wiki/

Specifications:
 - QCA9331 @ 400 MHz (MIPS 24Kc Big-Endian Processor)
 - 64MB of DDR2 RAM running at 400 MHz
 - 16MB of on-board flash storage
 - Support for USB 2.0
 - Support for Ethernet at 100 Mbps
 - 802.11b/g/n WiFi at 150 Mbps
 - 18 digital GPIOs
 - A single Serial UART
 - Support for SPI
 - Support for I2S

Flash instructions:
The device is running OpenWrt upon release using the ar71xx target.
Both a sysupgrade
and uploading the factory image using u-boots web-UI do work fine.

Depending on the ssh client, it might be necessary to enable outdated
KeyExchange methods e.g. in the clients ssh-config:

Host 192.168.1.1
        KexAlgorithms +diffie-hellman-group1-sha1

The stock credentials are: root onioneer

For u-boots web-UI manually configure `192.168.1.2/24` on your computer,
connect to `192.168.1.1`.

MAC addresses as verified by OEM firmware:
2G       phy0      label
LAN      eth0      label - 1

LAN is only available in combination with an optional expansion dock.

Based on vendor acked commit:
commit 5cd49bb067ca ("ar71xx: add support for Onion Omega")

Partly reverts:
commit fc553c7e4c8e ("ath79: drop unused/incomplete dts")

Signed-off-by: Jan-Niklas Burfeind <git@aiyionpri.me>
(cherry picked from commit d98738b5c118fc45068b45f07b8b6938e91f35d2)

target/linux/ath79/dts/ar9331_onion_omega.dts

@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+
+#include "ar9331.dtsi"
+
+#include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/input/input.h>
+
+/ {
+	model = "Onion Omega";
+	compatible = "onion,omega", "qca,ar9331";
+
+	aliases {
+		serial0 = &uart;
+		label-mac-device = &wmac;
+		led-boot = &led_system;
+		led-failsafe = &led_system;
+		led-running = &led_system;
+		led-upgrade = &led_system;
+	};
+
+	leds {
+		compatible = "gpio-leds";
+
+		led_system: system {
+			label = "amber:system";
+			gpios = <&gpio 27 GPIO_ACTIVE_LOW>;
+		};
+	};
+
+	keys {
+		compatible = "gpio-keys";
+
+		reset {
+			label = "reset";
+			linux,code = <KEY_RESTART>;
+			gpios = <&gpio 11 GPIO_ACTIVE_HIGH>;
+			debounce-interval = <60>;
+		};
+	};
+
+	reg_usb_vbus: reg_usb_vbus {
+		compatible = "regulator-fixed";
+		regulator-name = "usb_vbus";
+		regulator-min-microvolt = <5000000>;
+		regulator-max-microvolt = <5000000>;
+		gpio = <&gpio 8 GPIO_ACTIVE_HIGH>;
+		enable-active-high;
+	};
+};
+
+&ref {
+	clock-frequency = <25000000>;
+};
+
+&usb {
+	status = "okay";
+
+	vbus-supply = <&reg_usb_vbus>;
+	dr_mode = "host";
+};
+
+&usb_phy {
+	status = "okay";
+};
+
+&eth0 {
+	status = "okay";
+
+	compatible = "syscon", "simple-mfd";
+};
+
+&eth1 {
+	status = "okay";
+
+	mtd-mac-address = <&uboot 0x1fc00>;
+	mtd-mac-address-increment = <(-1)>;
+
+	gmac-config {
+		device = <&gmac>;
+		switch-phy-addr-swap = <4>;
+		switch-phy-swap = <4>;
+	};
+};
+
+&spi {
+	status = "okay";
+
+	flash@0 {
+		compatible = "jedec,spi-nor";
+		spi-max-frequency = <25000000>;
+		reg = <0>;
+
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			uboot: partition@0 {
+				label = "u-boot";
+				reg = <0x000000 0x020000>;
+				read-only;
+			};
+
+			partition@20000 {
+				compatible = "tplink,firmware";
+				label = "firmware";
+				reg = <0x020000 0xfd0000>;
+			};
+
+			art: partition@ff0000 {
+				label = "art";
+				reg = <0xff0000 0x010000>;
+				read-only;
+			};
+		};
+	};
+};
+
+&wmac {
+	status = "okay";
+
+	mtd-cal-data = <&art 0x1000>;
+
+	mtd-mac-address = <&uboot 0x1fc00>;
+};

target/linux/ath79/generic/base-files/etc/board.d/02_network

@@ -46,6 +46,7 @@ ath79_setup_interfaces()
 	netgear,ex7300|\
 	ocedo,koala|\
 	ocedo,raccoon|\
+	onion,omega|\
 	openmesh,mr600-v1|\
 	openmesh,mr600-v2|\
 	openmesh,mr900-v1|\

target/linux/ath79/image/generic.mk

@@ -1603,6 +1603,19 @@ define Device/ocedo_ursus
 endef
 TARGET_DEVICES += ocedo_ursus
 
+define Device/onion_omega
+  $(Device/tplink-16mlzma)
+  SOC := ar9331
+  DEVICE_VENDOR := Onion
+  DEVICE_MODEL := Omega
+  DEVICE_PACKAGES := kmod-usb-chipidea2
+  SUPPORTED_DEVICES += onion-omega
+  KERNEL_INITRAMFS := kernel-bin | append-dtb | lzma | uImage lzma
+  IMAGE_SIZE := 16192k
+  TPLINK_HWID := 0x04700001
+endef
+TARGET_DEVICES += onion_omega
+
 define Device/openmesh_common_64k
   DEVICE_VENDOR := OpenMesh
   DEVICE_PACKAGES := uboot-envtools