bcm96753ref: add initial support

This add the initial support of the broadcom reference
board bcm96753ref with a bcm6753 SoC.

This board has 1 GB of RAM, 256 MB of flash (nand),
2 USB port, 1 UART, and 4 ethernet ports.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
diff --git a/arch/arm/dts/bcm96753ref.dts b/arch/arm/dts/bcm96753ref.dts
new file mode 100644
index 0000000..e27a5b5
--- /dev/null
+++ b/arch/arm/dts/bcm96753ref.dts
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2022 Philippe Reynes <philippe.reynes@softathome.com>
+ */
+
+/dts-v1/;
+
+#include "bcm6753.dtsi"
+
+#include <dt-bindings/gpio/gpio.h>
+
+/ {
+	model = "Broadcom bcm6753ref";
+	compatible = "broadcom,bcm6753ref", "brcm,bcm6753";
+
+	aliases {
+		serial0 = &uart0;
+	};
+
+	chosen {
+		stdout-path = "serial0:115200n8";
+	};
+
+	memory {
+		device_type = "memory";
+		reg = <0x0 0x40000000>;
+	};
+};
+
+&uart0 {
+	u-boot,dm-pre-reloc;
+	status = "okay";
+};
+
+&gpio0 {
+	status = "okay";
+};
+
+&gpio1 {
+	status = "okay";
+};
+
+&gpio2 {
+	status = "okay";
+};
+
+&gpio3 {
+	status = "okay";
+};
+
+&gpio4 {
+	status = "okay";
+};
+
+&gpio5 {
+	status = "okay";
+};
+
+&gpio6 {
+	status = "okay";
+};
+
+&gpio7 {
+	status = "okay";
+};
+
+&nand {
+	status = "okay";
+	write-protect = <0>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	nandcs@0 {
+		compatible = "brcm,nandcs";
+		reg = <0>;
+		nand-ecc-strength = <4>;
+		nand-ecc-step-size = <512>;
+		brcm,nand-oob-sector-size = <16>;
+	};
+};