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/Kconfig b/arch/arm/Kconfig
index 6ce683a..8c7f317 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -2213,6 +2213,7 @@
 source "board/armltd/vexpress64/Kconfig"
 source "board/cortina/presidio-asic/Kconfig"
 source "board/broadcom/bcm963158/Kconfig"
+source "board/broadcom/bcm96753ref/Kconfig"
 source "board/broadcom/bcm968360bg/Kconfig"
 source "board/broadcom/bcm968580xref/Kconfig"
 source "board/broadcom/bcmns3/Kconfig"
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index 960f1a9..e53ad53 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -1104,6 +1104,9 @@
 dtb-$(CONFIG_ARCH_BCM68360) += \
 	bcm968360bg.dtb
 
+dtb-$(CONFIG_ARCH_BCM6753) += \
+	bcm96753ref.dtb
+
 dtb-$(CONFIG_ARCH_BCM6858) += \
 	bcm968580xref.dtb
 
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>;
+	};
+};