sandbox: Build a device tree file for sandbox

Add support for building a device tree for sandbox's CONFIG_OF_HOSTFILE
option to make it easier to use device tree with sandbox.

This adjusts the Makefile to build a u-boot.dtb file which can be passed
to sandbox U-Boot with:

   ./u-boot -d u-boot.dtb

Signed-off-by: Simon Glass <sjg@chromium.org>

Makefile

@@ -708,6 +708,7 @@ ALL-$(CONFIG_SPL) += spl/u-boot-spl.bin
 ALL-$(CONFIG_SPL_FRAMEWORK) += u-boot.img
 ALL-$(CONFIG_TPL) += tpl/u-boot-tpl.bin
 ALL-$(CONFIG_OF_SEPARATE) += u-boot.dtb u-boot-dtb.bin
+ALL-$(CONFIG_OF_HOSTFILE) += u-boot.dtb
 ifneq ($(CONFIG_SPL_TARGET),)
 ALL-$(CONFIG_SPL) += $(CONFIG_SPL_TARGET:"%"=%)
 endif

arch/sandbox/config.mk

@@ -11,3 +11,5 @@ __HAVE_ARCH_GENERIC_BOARD := y
 cmd_u-boot__ = $(CC) -o $@ -T u-boot.lds \
 	-Wl,--start-group $(u-boot-main) -Wl,--end-group \
 	$(PLATFORM_LIBS) -Wl,-Map -Wl,u-boot.map
+
+CONFIG_ARCH_DEVICE_TREE := sandbox

arch/sandbox/dts/Makefile

@@ -0,0 +1,11 @@
+dtb-$(CONFIG_SANDBOX) += sandbox.dtb
+
+targets += $(dtb-y)
+
+DTC_FLAGS += -R 4 -p 0x1000
+
+PHONY += dtbs
+dtbs: $(addprefix $(obj)/, $(dtb-y))
+	@:
+
+clean-files := *.dtb

arch/sandbox/dts/sandbox.dts

@@ -0,0 +1,20 @@
+/dts-v1/;
+
+/ {
+	triangle {
+		compatible = "demo-shape";
+		colour = "cyan";
+		sides = <3>;
+		character = <83>;
+	};
+	square {
+		compatible = "demo-shape";
+		colour = "blue";
+		sides = <4>;
+	};
+	hexagon {
+		compatible = "demo-simple";
+		colour = "white";
+		sides = <6>;
+	};
+};

include/configs/sandbox.h

@@ -32,6 +32,7 @@
 #define CONFIG_FIT_SIGNATURE
 #define CONFIG_RSA
 #define CONFIG_CMD_FDT
+#define CONFIG_DEFAULT_DEVICE_TREE	sandbox
 
 #define CONFIG_FS_FAT
 #define CONFIG_FS_EXT4