As raised in #6982, we need to better explain newcomers how to build applications using the auto_init modules.
This is the case for examples/default and for the networking specific examples (gnrc_networking, microcoap, nanocoap, gcoap, etc).

The idea is to create a common doxygen page explaining the principles of auto_init and listing all devices that support it. Then in the README files of concerned examples, add a link to this page.