ramips: add support for SNR SNR-CPE-ME2-Lite

SNR SNR-CPE-ME2-Lite is a 2.4/5 GHz band 11ac (Wi-Fi 5) router, based on MT7621A.

Specification:
    - SoC           : MediaTek MT7621A
    - RAM           : DDR3 128 MiB
    - Flash         : SPI-NOR 16 MiB
    - WLAN          : 2.4 GHz 2T2R (MediaTek MT7603E)
                      5 GHz 2T2R (MediaTek MT7613BE)
    - Ethernet      : 10/100/1000 Mbps x5
      - Switch      : MediaTek MT7530 (SoC)
    - UART          : through-hole on PCB
      - J4: 3.3V, GND, TX, RX
      - 57600n8
    - Power         : 12 VDC, 1.5 A

Flash instruction via WEB (firmware 1.10.4 and later)
    1. Boot SNR-CPE-ME2-Lite normally with "Router" mode
    2. Access to "http://192.168.1.1/" and open "Administration -> Management" page
    3. Select the OpenWrt factory image in "Firmware update" section and click "Update" button
    4. Wait ~120 seconds to complete flashing

Flash instruction via TFTP (all version):
    1. Boot SNR-CPE-ME2-Lite to recovery mode (hold the reset button while power on)
    2. Send firmware via TFTP client:
       TFTP Server address: 192.168.1.1
       TFTP Client address: 192.168.1.131
    3. Wait ~120 seconds to complete flashing

Signed-off-by: Alexey Kosmakov <a.kosmakov@nagtech.ru>

target/linux/ramips/dts/mt7621_snr_snr-cpe-me2-lite.dts

@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+#include "mt7621.dtsi"
+
+#include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/input/input.h>
+#include <dt-bindings/leds/common.h>
+
+/ {
+	compatible = "snr,snr-cpe-me2-lite", "mediatek,mt7621-soc";
+	model = "SNR-CPE-ME2-Lite";
+
+	leds {
+		compatible = "gpio-leds";
+
+		led_sys: led-0 {
+			label = "green:sys";
+			color = <LED_COLOR_ID_GREEN>;
+			function = LED_FUNCTION_STATUS;
+			gpios = <&gpio 15 GPIO_ACTIVE_HIGH>;
+		};
+
+		led_vpn: led-1 {
+			label = "green:vpn";
+			color = <LED_COLOR_ID_GREEN>;
+			function = LED_FUNCTION_STATUS;
+			gpios = <&gpio 14 GPIO_ACTIVE_LOW>;
+		};
+	};
+
+	keys {
+		compatible = "gpio-keys";
+
+		reset {
+			label = "reset";
+			gpios = <&gpio 18 GPIO_ACTIVE_LOW>;
+			linux,code = <KEY_RESTART>;
+		};
+	};
+};
+
+&state_default {
+	gpio {
+		groups = "jtag", "wdt";
+		function = "gpio";
+	};
+};
+
+&gdma {
+	status = "okay";
+};
+
+&spi0 {
+	status = "okay";
+
+	flash@0 {
+		compatible = "jedec,spi-nor";
+		reg = <0>;
+		spi-max-frequency = <104000000>;
+
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			partition@0 {
+				label = "u-boot";
+				reg = <0x0 0x30000>;
+				read-only;
+			};
+
+			partition@30000 {
+				label = "config";
+				reg = <0x30000 0x10000>;
+			};
+
+			factory: partition@40000 {
+				label = "factory";
+				reg = <0x40000 0x10000>;
+				read-only;
+			};
+
+			partition@50000 {
+				compatible = "denx,uimage";
+				label = "firmware";
+				reg = <0x50000 0xfb0000>;
+			};
+		};
+	};
+};
+
+&sdhci {
+	status = "okay";
+};
+
+&mdio {
+	ethphy0: ethernet-phy@0 {
+		reg = <0>;
+	};
+};
+
+&gmac0 {
+	nvmem-cells = <&macaddr_factory_e000>;
+	nvmem-cell-names = "mac-address";
+};
+
+&gmac1 {
+	status = "okay";
+	label = "wan";
+	phy-handle = <&ethphy0>;
+
+	nvmem-cells = <&macaddr_factory_e006>;
+	nvmem-cell-names = "mac-address";
+};
+
+&switch0 {
+	ports {
+		port@1 {
+			status = "okay";
+			label = "lan1";
+		};
+
+		port@2 {
+			status = "okay";
+			label = "lan2";
+		};
+
+		port@3 {
+			status = "okay";
+			label = "lan3";
+		};
+
+		port@4 {
+			status = "okay";
+			label = "lan4";
+		};
+	};
+};
+
+&pcie {
+	status = "okay";
+};
+
+&pcie0 {
+	wifi@0,0 {
+		compatible = "mediatek,mt76";
+		reg = <0x0000 0 0 0 0>;
+		mediatek,mtd-eeprom = <&factory 0x0000>;
+		ieee80211-freq-limit = <2400000 2500000>;
+	};
+};
+
+&pcie1 {
+	wifi@0,0 {
+		compatible = "mediatek,mt76";
+		reg = <0x0000 0 0 0 0>;
+		mediatek,mtd-eeprom = <&factory 0x8000>;
+		ieee80211-freq-limit = <5000000 6000000>;
+	};
+};
+
+&factory {
+	compatible = "nvmem-cells";
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	macaddr_factory_e000: macaddr@e000 {
+		reg = <0xe000 0x6>;
+	};
+
+	macaddr_factory_e006: macaddr@e006 {
+		reg = <0xe006 0x6>;
+	};
+};

target/linux/ramips/image/mt7621.mk

@@ -1723,6 +1723,17 @@ define Device/sercomm_na502s
 endef
 TARGET_DEVICES += sercomm_na502s
 
+define Device/snr_snr-cpe-me2-lite
+  $(Device/dsa-migration)
+  $(Device/uimage-lzma-loader)
+  IMAGE_SIZE := 16064k
+  DEVICE_VENDOR := SNR
+  DEVICE_MODEL := SNR-CPE-ME2-Lite
+  UIMAGE_NAME := $$(DEVICE_MODEL)
+  DEVICE_PACKAGES := kmod-mt7603 kmod-mt7615e kmod-mt7663-firmware-ap
+endef
+TARGET_DEVICES += snr_snr-cpe-me2-lite
+
 define Device/storylink_sap-g3200u3
   $(Device/dsa-migration)
   IMAGE_SIZE := 7872k