mips: mtmips: add two reference boards for mt7621

The mt7621_rfb board supports integrated giga PHYs plus one external
giga PHYs. It also has up to 512MiB DDR3, 16MB SPI-NOR, 3 mini PCI-e x1
slots, SDXC and USB.

The mt7621_nand_rfb board is almost the same as mt7621_rfb board, but it
uses NAND flash and SDXC is not available.

Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/mips/dts/mediatek,mt7621-nand-rfb.dts b/arch/mips/dts/mediatek,mt7621-nand-rfb.dts
new file mode 100644
index 0000000..67ba298
--- /dev/null
+++ b/arch/mips/dts/mediatek,mt7621-nand-rfb.dts
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 MediaTek Inc. All rights reserved.
+ *
+ * Author: Weijie Gao <weijie.gao@mediatek.com>
+ */
+
+/dts-v1/;
+
+#include "mt7621.dtsi"
+
+/ {
+	compatible = "mediatek,mt7621-nand-rfb", "mediatek,mt7621-soc";
+	model = "MediaTek MT7621 RFB (NAND)";
+
+	aliases {
+		serial0 = &uart0;
+	};
+
+	chosen {
+		stdout-path = &uart0;
+	};
+};
+
+&pinctrl {
+	state_default: pin_state {
+		nand {
+			groups = "spi", "sdxc";
+			function = "nand";
+		};
+
+		gpios {
+			groups = "i2c", "uart3", "pcie reset";
+			function = "gpio";
+		};
+
+		wdt {
+			groups = "wdt";
+			function = "wdt rst";
+		};
+
+		jtag {
+			groups = "jtag";
+			function = "jtag";
+		};
+	};
+};
+
+&uart0 {
+	status = "okay";
+};
+
+&gpio {
+	status = "okay";
+};
+
+&eth {
+	status = "okay";
+};
+
+&ssusb {
+	status = "okay";
+};
+
+&u3phy {
+	status = "okay";
+};