Support for Overlays in target dependent code

Hi,

I am working on Xtensa architecture (gdb-7.*/gdb/xtensa-tdep.c). I wish 
to add overlay support for Xtensa. Seeing other similar architectures, I 
believe the only addition required for overlay support to seamlessly 
work (assuming no other changes in other target dependent code) would be:

set_gdbarch_overlay_update (gdbarch, simple_overlay_update);

in <target>_gdbarch_init(), just as is the case with regards to ARM and 
MIPS.

Is anything else required too?

Thanks!
Tejas