Tools
What is needed to convert troff documents from DocBook:
To Do
List the document that have yet to be converted here.
XKB specs (xorg-docs/specs/XKB/Proto & xorg-docs/specs/XKB/XKBlib): these are in FrameMaker format. AlanCoopersmith used FrameMaker's Export options to produce several more convertible formats from them: XML (with unknown DTD), HTML & MIF - available at http://people.freedesktop.org/~alanc/xkb/ - but someone needs to finish converting to DocBook/XML.
Ongoing
There has been an interest in converting the parts of the Xorg documentation written in troff to DocBook (or any other generic format). In order not to duplicate efforts, here is the list of what is being done and by whom.
PeterHutterer has converted the XInput documentation to DocBook
FrancoisDenisGonthier and MichaelVerret are trying to convert from XProtocol from troff to DocBook using doclifter.
GüntherBrammer is converting documentation in the Xext directory.