The latest documentation can be found at: http://adafruit-micropython.readthedocs.io/en/latest/

The documentation you see there is generated from the files in the whole tree: https://github.com/adafruit/micropython/tree/master

If you're making changes to the documentation, you should build the documentation locally so that you can preview your changes.

Install Sphinx, and optionally (for the RTD-styling), sphinx_rtd_theme, preferably in a virtualenv:

 pip install sphinx
 pip install sphinx_rtd_theme

In micropython/, build the docs:

sphinx-build -v -b html . _build/html

You'll find the index page at micropython/docs/_build/html/index.html.