-dtstree := $(srctree)/$(src)
-dtb-$(CONFIG_OF_ALL_DTBS) := $(patsubst $(dtstree)/%.dts,%.dtb, $(wildcard $(dtstree)/*.dts))
-
-always := $(dtb-y)
-clean-files := *.dtb *.dtb.S
+# for CONFIG_OF_ALL_DTBS test
+dtstree := $(srctree)/$(src)
+dtb- := $(patsubst $(dtstree)/%.dts,%.dtb, $(wildcard $(dtstree)/*.dts))