Based on the kernel Documentation: Documentation/kbuild/modules. TXT: Building External modules section 5 describes position description
can be determined as follows:

--- 5.1 INSTALL_MOD_PATH

	Above are the default directories but as always some level of
	customization is possible. A prefix can be added to the
	installation path using the variable INSTALL_MOD_PATH:

		$ make INSTALL_MOD_PATH=/frodo modules_install
		=> Install dir: /frodo/lib/modules/$(KERNELRELEASE)/kernel/

	INSTALL_MOD_PATH may be set as an ordinary shell variable or,
	as shown above, can be specified on the command line when
	calling "make." This has effect when installing both in-tree
	and out-of-tree modules.

--- 5.2 INSTALL_MOD_DIR

	External modules are by default installed to a directory under
	/lib/modules/$(KERNELRELEASE)/extra/, but you may wish to
	locate modules for a specific functionality in a separate
	directory. For this purpose, use INSTALL_MOD_DIR to specify an
	alternative name to "extra."

		$ make INSTALL_MOD_DIR=gandalf -C $KDIR \
		       M=$PWD modules_install
		=> Install dir: /lib/modules/$(KERNELRELEASE)/gandalf/