kbuild: Add support to build overlays (%.dtbo)

Add support for building DT overlays (%.dtbo). The overlay's source file
will have the usual extension, i.e. .dts, though the blob will have
.dtbo extension to distinguish it from normal blobs.
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/434ba2467dd0cd011565625aeb3450650afe0aae.1611904394.git.viresh.kumar@linaro.org

.gitignore

@@ -18,6 +18,7 @@
 *.c.[012]*.*
 *.dt.yaml
 *.dtb
+*.dtbo
 *.dtb.S
 *.dwo
 *.elf

Makefile

@@ -1337,6 +1337,9 @@ ifneq ($(dtstree),)
 %.dtb: include/config/kernel.release scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
 
+%.dtbo: include/config/kernel.release scripts_dtc
+	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
+
 PHONY += dtbs dtbs_install dtbs_check
 dtbs: include/config/kernel.release scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree)
@@ -1816,7 +1819,7 @@ clean: $(clean-dirs)
 	@find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
 		\( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' \
 		-o -name '*.ko.*' \
-		-o -name '*.dtb' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
+		-o -name '*.dtb' -o -name '*.dtbo' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
 		-o -name '*.dwo' -o -name '*.lst' \
 		-o -name '*.su' -o -name '*.mod' \
 		-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \

scripts/Makefile.dtbinst

@@ -29,6 +29,9 @@ quiet_cmd_dtb_install = INSTALL $@
 $(dst)/%.dtb: $(obj)/%.dtb
 	$(call cmd,dtb_install)
 
+$(dst)/%.dtbo: $(obj)/%.dtbo
+	$(call cmd,dtb_install)
+
 PHONY += $(subdirs)
 $(subdirs):
 	$(Q)$(MAKE) $(dtbinst)=$@ dst=$(patsubst $(obj)/%,$(dst)/%,$@)

scripts/Makefile.lib

@@ -86,7 +86,9 @@ extra-$(CONFIG_OF_ALL_DTBS)	+= $(dtb-)
 
 ifneq ($(CHECK_DTBS),)
 extra-y += $(patsubst %.dtb,%.dt.yaml, $(dtb-y))
+extra-y += $(patsubst %.dtbo,%.dt.yaml, $(dtb-y))
 extra-$(CONFIG_OF_ALL_DTBS) += $(patsubst %.dtb,%.dt.yaml, $(dtb-))
+extra-$(CONFIG_OF_ALL_DTBS) += $(patsubst %.dtbo,%.dt.yaml, $(dtb-))
 endif
 
 # Add subdir path
@@ -327,6 +329,9 @@ cmd_dtc = $(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ;
 $(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE
 	$(call if_changed_dep,dtc)
 
+$(obj)/%.dtbo: $(src)/%.dts $(DTC) FORCE
+	$(call if_changed_dep,dtc)
+
 DT_CHECKER ?= dt-validate
 DT_BINDING_DIR := Documentation/devicetree/bindings
 # DT_TMP_SCHEMA may be overridden from Documentation/devicetree/bindings/Makefile