arm: bcmbca: add bcm6878 SoC support

BCM6878 is an ARM A7 based PON Broadband SoC. It is part of the BCA
(Broadband Carrier Access origin) chipset family so it's added under
ARCH_BCMBCA platform. This initial support includes a bare-bone
implementation and dts with CPU subsystem, memory and ARM PL011
uart.

This SoC is supported in the linux-next git repository so the dts and
dtsi files are copied from linux with minor fix-up that needs to be
upstreamed to linux as well.

The u-boot image can be loaded from flash or network to the entry point
address in the memory and boot from there.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
diff --git a/arch/arm/mach-bcmbca/bcm6878/Kconfig b/arch/arm/mach-bcmbca/bcm6878/Kconfig
new file mode 100644
index 0000000..43f8942
--- /dev/null
+++ b/arch/arm/mach-bcmbca/bcm6878/Kconfig
@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# (C) Copyright 2022 Broadcom Ltd
+#
+
+if BCM6878
+
+config TARGET_BCM96878
+	bool "Broadcom 6878 Reference Board"
+	depends on ARCH_BCMBCA
+
+config SYS_SOC
+	default "bcm6878"
+
+source "board/broadcom/bcmbca/Kconfig"
+
+endif
diff --git a/arch/arm/mach-bcmbca/bcm6878/Makefile b/arch/arm/mach-bcmbca/bcm6878/Makefile
new file mode 100644
index 0000000..beb979a
--- /dev/null
+++ b/arch/arm/mach-bcmbca/bcm6878/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# (C) Copyright 2022 Broadcom Ltd
+#
+obj- += dummy.o