dtbo: make dtbos special

Special rule for dtbo generation
Signed-off-by: NPantelis Antoniou <pantelis.antoniou@konsulko.com>
Acked-by: NSimon Glass <sjg@chromium.org>

scripts/Makefile.lib

@@ -321,6 +321,23 @@ $(obj)/%.dtb: $(src)/%.dts FORCE
 
 dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)
 
+# DTCO
+# ---------------------------------------------------------------------------
+
+quiet_cmd_dtco = DTCO    $@
+# Rule for objects only; does not put specific u-boot include at the end
+# No generation of assembly file either
+# Modified for U-Boot
+cmd_dtco = mkdir -p $(dir ${dtc-tmp}) ; \
+	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) - ; \
+	$(DTC) -@ -O dtb -o $@ -b 0 \
+		-i $(dir $<) $(DTC_FLAGS) \
+		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
+	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
+
+$(obj)/%.dtbo: $(src)/%.dts FORCE
+	$(call if_changed_dep,dtco)
+
 # Fonts
 # ---------------------------------------------------------------------------