-KERNEL:=2.$(word 2,$(subst ., ,$(strip $(LINUX_VERSION))))
-KERNEL_PATCHVER:=$(shell echo $(LINUX_VERSION) | cut -d. -f1,2,3 | cut -d- -f1)
+KERNEL?=2.$(word 2,$(subst ., ,$(strip $(LINUX_VERSION))))
+KERNEL_PATCHVER=$(shell echo $(LINUX_VERSION) | cut -d. -f1,2,3 | cut -d- -f1)