[$] Maintainers Summit: SPDX, cross-subsystem development, and conclusion

The 2017 Maintainers Summit, the first event of its type, managed to cover awide range of topics in a single half-day. This article, which concludesLWN's coverage of this event, picks up a fewrelatively short topics that were discussed toward the end of the session.These include a new initiative to add SPDX license tags to the kernel, theperils of cross-subsystem development, and an evaluation of the summititself.