Texinfo is the official documentation format of the GNU project. It was invented by Richard Stallman and Bob Chassell many years ago, based on Brian Reid's Scribe and other formatting languages of the time. It is used by many non-GNU projects as well.
The basics:
Anyone is welcome to subscribe to any or all of these. Do so by sending a message to the corresponding -request address, for example bug-texinfo-request@gnu.org. A single line
subscribe yourusername@yourdomain.domin both the body and the subject works best.