dts: generate multiple device tree blobs

It is convenient to have all device trees on the same SoC compiled.
It allows for later easy repackaging without the need to re-run
the make file.

  - Build device trees with the same SoC under arch/$(ARCH)/dts

  - Copy the one specified by CONFIG_DEFAULT_DEVICE_TREE or
    DEVICE_TREE=... to dts/dt.dtb

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/microblaze/dts/Makefile b/arch/microblaze/dts/Makefile
new file mode 100644
index 0000000..6d4a11f
--- /dev/null
+++ b/arch/microblaze/dts/Makefile
@@ -0,0 +1,11 @@
+dtb-y += microblaze-generic.dtb
+
+targets += $(dtb-y)
+
+DTC_FLAGS += -R 4 -p 0x1000
+
+PHONY += dtbs
+dtbs: $(addprefix $(obj)/, $(dtb-y))
+	@:
+
+clean-files := *.dtb