MKDOG (MaKefile DOcumentation Generator) is documentation generator for Makefiles. It is intended for documenting projects which, at most, use GNU make as main engine.
MKDOG extracts description of Makefile entries (rules, variable assignments) from especially formatted comments above an entries and outputs HTML document with index and search capability.
MKDOG is written on Python as Sphinx extension.
MKDOG is available under the terms of the GNU GENERAL PUBLIC LICENSE version 3, see LICENSE for more information.
There are some other open-source documentation generators exists that claims Makefile support:
but really Makefile support is not documented well and it is at very basic level.