kbuild: more doc. cleanups

	   --- 6.1 Set variables to tweak the build to the architecture

	   --- 6.2 Add prerequisites to archprepare:

	   --- 6.3 List directories to visit when descending

	   --- 6.4 Architecture specific boot images

	   --- 6.4 Architecture-specific boot images

	   --- 6.5 Building non-kbuild targets

	   --- 6.6 Commands useful for building a boot image

	   --- 6.7 Custom kbuild commands

	Example:

		obj-y += foo.o

	This tell kbuild that there is one object in that directory, named

	This tells kbuild that there is one object in that directory, named

	foo.o. foo.o will be built from foo.c or foo.S.

	If foo.o shall be built as a module, the variable obj-m is used.

	Special rules are used when the kbuild infrastructure does

	not provide the required support. A typical example is

	header files generated during the build process.

	Another example are the architecture specific Makefiles which

	Another example are the architecture-specific Makefiles which

	need special rules to prepare boot images etc.

	Special rules are written as normal Make rules.

		#arch/i386/kernel/Makefile

		vsyscall-flags += $(call ld-option, -Wl$(comma)--hash-style=sysv)

	In the above example vsyscall-flags will be assigned the option

	In the above example, vsyscall-flags will be assigned the option

	-Wl$(comma)--hash-style=sysv if it is supported by $(CC).

	The second argument is optional, and if supplied will be used

	if first argument is not supported.

		#arch/i386/Makefile

		cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)

	In the above example cflags-y will be assigned the option

	In the above example, cflags-y will be assigned the option

	-march=pentium-mmx if supported by $(CC), otherwise -march=i586.

	The second argument to cc-option is optional, and if omitted,

	cflags-y will be assigned no value if first option is not supported.

   located at the root of the obj tree.

   The very first objects linked are listed in head-y, assigned by

   arch/$(ARCH)/Makefile.

7) Finally, the architecture specific part does any required post processing

7) Finally, the architecture-specific part does any required post processing

   and builds the final bootimage.

   - This includes building boot records

   - Preparing initrd images and the like

	$(head-y) lists objects to be linked first in vmlinux.

	$(libs-y) lists directories where a lib.a archive can be located.

	The rest lists directories where a built-in.o object file can be

	The rest list directories where a built-in.o object file can be

	located.

	$(init-y) objects will be located after $(head-y).

	$(core-y), $(libs-y), $(drivers-y) and $(net-y).

	The top level Makefile defines values for all generic directories,

	and arch/$(ARCH)/Makefile only adds architecture specific directories.

	and arch/$(ARCH)/Makefile only adds architecture-specific directories.

	Example:

		#arch/sparc64/Makefile

		drivers-$(CONFIG_OPROFILE)  += arch/sparc64/oprofile/

--- 6.4 Architecture specific boot images

--- 6.4 Architecture-specific boot images

	An arch Makefile specifies goals that take the vmlinux file, compress

	it, wrap it in bootstrapping code, and copy the resulting files

	"$(Q)$(MAKE) $(build)=<dir>" is the recommended way to invoke

	make in a subdirectory.

	There are no rules for naming architecture specific targets,

	There are no rules for naming architecture-specific targets,

	but executing "make help" will list all relevant targets.

	To support this, $(archhelp) must be defined.

			$(call if_changed,ld/objcopy/gzip)

	When the rule is evaluated, it is checked to see if any files

	needs an update, or the command line has changed since the last

	need an update, or the command line has changed since the last

	invocation. The latter will force a rebuild if any options

	to the executable have changed.

	Any target that utilises if_changed must be listed in $(targets),

	                  assignment.

	The kbuild infrastructure for *lds file are used in several

	architecture specific files.

	architecture-specific files.

=== 7 Kbuild Variables

	This variable defines a place for the arch Makefiles to install

	the resident kernel image and System.map file.

	Use this for architecture specific install targets.

	Use this for architecture-specific install targets.

    INSTALL_MOD_PATH, MODLIB