Kconfig migration: modelling of provided features

Dear RIOTers,

As part of the ongoing effort of the Configuration Task Force[1] towards using Kconfig as the default configuration tool in RIOT, the provided features of boards, CPUs and architectures have been modelled in Kconfig (the process has been tracked using a GitHub project[2]). In order to keep the Makefiles and the Kconfig files synchronized a test has been added[3]. This part of the migration concluded with #14541[4], which made mandatory for all boards to have a Kconfig file selecting the provided features.

From the contribution perspective this means that from now on: - Changes in the provided features should be done both in Makefile.features and Kconfig file - Boards, Boards' common, CPUs, CPUs' common and architectures should have their Kconfig files selecting the provided features and assigning default values to common symbols

For more information on how to write these Kconfig files please refer to this "Kconfig in RIOT" documentation section[5].

Best regards, Leandro.

[1]: https://github.com/RIOT-OS/RIOT/issues/9856 [2]: https://github.com/RIOT-OS/RIOT/projects/27 [3]: https://github.com/RIOT-OS/RIOT/blob/master/tests/kconfig_features/README.md [4]: https://github.com/RIOT-OS/RIOT/pull/14541 [5]: http://doc.riot-os.org/kconfig-in-riot.html#kconfig-cpu-boards-features