Hi, I’m sorry, but I’m really no expert regarding porting of boards. It is propably best to refer to the (hopefully not so outdated) porting guide , but I’m forwarding your message to the devel mailinglist, so people that have a better idea of it can read it. Regarding posting to a RIOT mailing list: just write an E-Mail to email@example.com as I did with this mail and it will be posted to the mailing list. For subscribing go to  and enter the necessary information in the “Subscribe” section.
Hope I could help, Martine
 https://github.com/RIOT-OS/RIOT/wiki/Porting-Guide  https://lists.riot-os.org/mailman/listinfo/devel