Makefile

The Makefile in the root of the Linux kernel source tree is essentially used to build

vmlinux (the resident kernel image), and
module files
documentation (generated in Documentation/output from files under Documentation/)
other development related stuff like tag files etc.

The top level Makefile includes arch/$SRCARCH/Makefile which supplies architecture-specific information to the top Makefile.

Version variables

The top of the Makefile defines a few version related variables:

VERSION = 6
PATCHLEVEL = 5
SUBLEVEL = 0
EXTRAVERSION = -rc7
NAME = Hurr durr I'ma ninja sloth

$ make -s kernelversion
6.5.0-rc7

Compare with include/config/kernel.release (if it exists) and include/generated/uapi/linux/version.h (if it exists).

`scripts/Kbuild.include`	Definition of convenience variables such as `comma`, `quote` etc., comparison macros (`test-ge`, `test-lt`) and more such stuff
`scripts/subarch.include`	Assign value to `SUBARCH`
`scripts/Makefile.clang`	if `CC_VERSION_TEXT` contains `clang`
`scripts/Makefile.compiler`	If `need-compiler` is defined
`arch/$(SRCARCH)/Makefile`	For example `arch/x86/Makefile`
`include/config/auto.conf`	If `need-config` is defined.
`scripts/Makefile.extrawarn`
`scripts/Makefile.debug`	if `CONFIG_DEBUG_INFO` = `y`
`scripts/Makefile.btf`	if `CONFIG_DEBUG_INFO_BTF` = `y`
`scripts/Makefile.kasan`	if `CONFIG_KASAN` = `y`
`scripts/Makefile.kcsan`	if `CONFIG_KCSAN` = `y`
`scripts/Makefile.kmsan`	if `CONFIG_KMSAN` = `y`
`scripts/Makefile.ubsan`	if `CONFIG_UBSAN` = `y`
`scripts/Makefile.kcov`	if `CONFIG_KCOV` = `y`
`scripts/Makefile.randstruct`	if `CONFIG_RANDSTRUCT` = `y`
`scripts/Makefile.gcc-plugins`	if `CONFIG_GCC_PLUGINS` = `y`