build: support for .dtbo files for dtb overlays

Kernel 4.4.6+ on RaspberryPi support .dtbo files for overlays, instead of .dtb.
Patch the kernel, which has faulty rules to generate .dtbo the way yocto does

Signed-off-by: Herve Jourdain <[email protected]>
Signed-off-by: Khem Raj <[email protected]>

Author: hjourdain

arch/arm/Makefile

@@ -336,6 +336,8 @@ $(INSTALL_TARGETS):
 
 %.dtb: | scripts
 	$(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $(boot)/dts/$@
+%.dtbo: | scripts
+	$(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $(boot)/dts/$@
 
 PHONY += dtbs dtbs_install
 

scripts/Makefile.lib

@@ -313,8 +313,9 @@ $(obj)/%.dtb: $(src)/%.dts FORCE
 	$(call if_changed_dep,dtc)
 
 quiet_cmd_dtco = DTCO    $@
-cmd_dtco = $(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
-	$(objtree)/scripts/dtc/dtc -@ -H epapr -O dtb -o $@ -b 0 \
+cmd_dtco = mkdir -p $(dir ${dtc-tmp}) ; \
+	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
+	$(DTC) -@ -H epapr -O dtb -o $@ -b 0 \
 		-i $(dir $<) $(DTC_FLAGS) \
 		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
 	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)