Pull documentation updates from Jonathan Corbet:
 "A relatively calm cycle for the docs tree again.

  - The old driver statement has been added to the kernel docs.

  - We have a couple of new helper scripts. find-unused-docs.sh from
    Sayli Karnic will point out kerneldoc comments that are not actually
    used in the documentation. Jani Nikula's
    documentation-file-ref-check finds references to non-existing files.

  - A new ftrace document from Steve Rostedt.

  - Vinod Koul converted the dmaengine docs to RST

  Beyond that, it's mostly simple fixes.

  This set reaches outside of Documentation/ a bit more than most. In
  all cases, the changes are to comment docs, mostly from Randy, in
  places where there didn't seem to be anybody better to take them"

* tag 'docs-4.15' of git://git.lwn.net/linux: (52 commits)
  documentation: fb: update list of available compiled-in fonts
  MAINTAINERS: update DMAengine documentation location
  dmaengine: doc: ...