I believe it is something like this:
default.ini : obviously the default key mappings
drivername.ini : applies only to games with this driver (eg neogeo.ini)
romname.ini : applies to 1 rom (& clones?)
You can also add this to default.ini:
dial_ini "dial.ini"
trackball_ini "trackball.ini"
lightgun_ini "lightgun.ini"
paddle_ini "paddle.ini"
ad_stick_ini "ad_stick.ini"
pedal_ini "pedal.ini"
(substitute the parts in "" 's for your prefered). These filenames refer to .ini's which are specific for the given input type.
Put all of those files in your \mame\ctrlr\ctrlrname folder and refer to the ctrlr name in your mame.ini.
I think that is right anyway
