xtensa: use new common dtc rule

The current rules have the .dtb files build in a different directory
from the .dts files. This patch changes xtensa to use the generic dtb
rule which builds .dtb files in the same directory as the source .dts.

This requires moving parts of arch/xtensa/boot/Makefile into newly
created arch/xtensa/boot/dts/Makefile, and updating arch/xtensa/Makefile
to call the new Makefile.
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NChris Zankel <chris@zankel.net>

arch/xtensa/Makefile

@@ -88,7 +88,7 @@ core-y		+= $(buildvar) $(buildplf)
 libs-y		+= arch/xtensa/lib/ $(LIBGCC)
 
 ifneq ($(CONFIG_BUILTIN_DTB),"")
-core-$(CONFIG_OF) += arch/xtensa/boot/
+core-$(CONFIG_OF) += arch/xtensa/boot/dts/
 endif
 
 boot		:= arch/xtensa/boot
@@ -101,7 +101,7 @@ zImage: vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $@
 
 %.dtb:
-	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
+	$(Q)$(MAKE) $(build)=$(boot)/dts $(boot)/dts/$@
 
 define archhelp
   @echo '* zImage      - Compressed kernel image (arch/xtensa/boot/images/zImage.*)'

arch/xtensa/boot/Makefile

@@ -25,18 +25,6 @@ bootdir-$(CONFIG_XTENSA_PLATFORM_ISS)	 += boot-elf
 bootdir-$(CONFIG_XTENSA_PLATFORM_XT2000) += boot-redboot boot-elf boot-uboot
 bootdir-$(CONFIG_XTENSA_PLATFORM_XTFPGA) += boot-redboot boot-elf boot-uboot
 
-
-BUILTIN_DTB := $(patsubst "%",%,$(CONFIG_BUILTIN_DTB)).dtb.o
-ifneq ($(CONFIG_BUILTIN_DTB),"")
-obj-$(CONFIG_OF) += $(BUILTIN_DTB)
-endif
-
-# Rule to build device tree blobs
-$(obj)/%.dtb: $(src)/dts/%.dts FORCE
-	$(call if_changed_dep,dtc)
-
-clean-files := *.dtb.S
-
 zImage Image: $(bootdir-y)
 
 $(bootdir-y): $(addprefix $(obj)/,$(subdir-y)) \

arch/xtensa/boot/dts/Makefile

+#
+# arch/xtensa/boot/dts/Makefile
+#
+# This file is subject to the terms and conditions of the GNU General Public
+# License.  See the file "COPYING" in the main directory of this archive
+# for more details.
+#
+#
+
+BUILTIN_DTB := $(patsubst "%",%,$(CONFIG_BUILTIN_DTB)).dtb.o
+ifneq ($(CONFIG_BUILTIN_DTB),"")
+obj-$(CONFIG_OF) += $(BUILTIN_DTB)
+endif
+
+clean-files := *.dtb.S