Konstantin Ryabitsev has put up a
blog entry showing how to use b4 to submit kernel patches
without (directly) using email.

While b4 started out as a way for maintainers to retrieve patches
from mailing lists, it also has contributor-oriented
features. Starting with version 0.10 b4 can:

• create and manage patch series and cover letters
• track and auto-reroll series revisions
• display range-diffs between revisions
• apply trailers received from reviewers and maintainers
• submit patches without needing a valid SMTP gateway

Source: LWN.net – Ryabitsev: Sending a kernel patch with b4 (part 1)