How to add symbol to be exported in lib/libc/arm/Symbol.map

Hello group!

I have a few questions regarding adding symbols to
lib/libc/<arch>/Symbol.map, so that function signatures are exported:
- what are the conventions regarding putting symbols in FBSD_X.Y or
FBSDprivate_X.Y sections of the aforementioned files?
- when it is necessary to bump X.Y numbers?
- what is the difference between FBSD_X.Y and FBSDprivate_X.Y sections?

The above questions arose from the discussion on freebsd-arm_at_
(http://lists.freebsd.org/pipermail/freebsd-arm/2012-June/003555.html)
which concerns fixing Perl on ARM. The fix is to add __flt_rounds
function signature to lib/libc/arm/Symbols.map. Regarding this fix it
appears (after Symbols.map files analysis and checking their SVN
history) that adding this symbol is just a bug fix and should be put to
FBSD_1.0 section without incrementing numbers. But I don't have more
in-depth explanation so sending this email.

Anyone can comment on the above questions or point to some documentation
(I've searched Developer's Handbook and Internet but found nothing)?

Regards,

Jan Sieka