Wikipedia
OpenEmbedded
OpenEmbedded is a software framework used for creating Linux distributions aimed for, but not restricted to, embedded devices. The build system is based on BitBake recipes, which behave like Gentoo Linux ebuilds.
Recipes in the old OpenEmbedded-Classic were all found in one place. In the new OpenEmbedded-Core, the structure has changed into meta layers to make adding custom recipes easier.
OpenEmbedded can be installed and automatically updated via Git.