There is a script in place to manage the deployment of Substrate rustdocs at
https://paritytech.github.io/substrate, which is pushing the rustdocs file in gh-pages branch of
https://github.com/paritytech/substrate.
The documentation at the top of the rustdocs-release.sh explains most of the mechanics of the script.
Manage the rustdocs deployment with one of the following commands.
# Deploy rustdocs of `monthly-2021-10` tag
.maintain/rustdocs-release.sh deploy monthly-2021-10
# In addition to the above, the `latest` symlink will point to this version of rustdocs
.maintain/rustdocs-release.sh deploy -l monthly-2021-10
# Remove the rustdocs of `monthly-2021-10` from `gh-pages`.
.maintain/rustdocs-release.sh remove monthly-2021-10