The MicroPython documentation can be found at: http://docs.micropython.org/en/latest/

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

If you're making changes to the documentation, you may want to 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/docs, build the docs:

make MICROPY_PORT=<port_name> BUILDDIR=build/<port_name> html

Where <port_name> can be unix, pyboard, wipy or esp8266.

You'll find the index page at micropython/docs/build/<port_name>/html/index.html.