Please define CONFIG_ARCH_DEVICE_TREE))
# We preprocess the device tree file provide a useful define
-DTS_CPPFLAGS := -DARCH_CPU_DTS=\"$(SRCTREE)/arch/$(ARCH)/dts/$(CONFIG_ARCH_DEVICE_TREE).dtsi\"
+DTS_CPPFLAGS := -DARCH_CPU_DTS=\"$(SRCTREE)/arch/$(ARCH)/dts/$(CONFIG_ARCH_DEVICE_TREE).dtsi\" \
+ -DBOARD_DTS=\"$(SRCTREE)/board/$(VENDOR)/$(BOARD)/dts/$(DEVICE_TREE).dts\"
all: $(obj).depend $(LIB)