linux: Add support to specify special Kernel Image make target

This is useful for ARCHes like PowerPC that have a whole lot of
special targets for each different board.  The kernel image target
tells make which OpenFirmware machine description file is combined into
the kernel binary.

[Peter: fix long lines]
Signed-Off-By:  Martin Hicks <mort@bork.org>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

linux/Config.in

@@ -133,8 +133,26 @@ config BR2_LINUX_KERNEL_VMLINUX
 	bool "vmlinux"
 	depends on BR2_mips || BR2_mipsel
 
+config BR2_LINUX_KERNEL_IMAGE_TARGET_CUSTOM
+	bool "custom target"
+	help
+	  For certain cases a board-specific target image must be
+	  used.  For example, on powerPC where the OpenFirmware
+	  description is attached in a board-specific kernel image
+	  target like 'cuImage.mpc8379_rdb'.
+
+	  Select this option and specify the make target in "Kernel
+	  image target name".
+
 endchoice
 
+config BR2_LINUX_KERNEL_IMAGE_TARGET_NAME
+	string "Kernel image target name"
+	depends on BR2_LINUX_KERNEL_IMAGE_TARGET_CUSTOM
+	help
+	  Specify the kernel make target to build the kernel that you
+	  need.
+
 endif # BR2_LINUX_KERNEL
 
 endmenu

linux/linux.mk

@@ -30,6 +30,9 @@ LINUX26_MAKE_FLAGS = \
 # going to be installed in the target filesystem.
 LINUX26_VERSION_PROBED = $(shell $(MAKE) $(LINUX26_MAKE_FLAGS) -C $(LINUX26_DIR) --no-print-directory -s kernelrelease)
 
+ifeq ($(BR2_LINUX_KERNEL_IMAGE_TARGET_CUSTOM),y)
+LINUX26_IMAGE_NAME=$(call qstrip,$(BR2_LINUX_KERNEL_IMAGE_TARGET_NAME))
+else
 ifeq ($(BR2_LINUX_KERNEL_UIMAGE),y)
 ifeq ($(KERNEL_ARCH),blackfin)
 # a uImage, but with a different file name
@@ -47,6 +50,7 @@ LINUX26_IMAGE_NAME=vmlinux.bin
 else ifeq ($(BR2_LINUX_KERNEL_VMLINUX),y)
 LINUX26_IMAGE_NAME=vmlinux
 endif
+endif
 
 # Compute the arch path, since i386 and x86_64 are in arch/x86 and not
 # in arch/$(KERNEL_ARCH). Even if the kernel creates symbolic links