I installed an additional info file using
install-info /usr/share/info/asymptote/asymptote.info.gz /usr/share/info/dir
it is perfectly visible by info command from the command line, i.e. info asymptote return content of asymptote/asymptote.info.gz properly. Also it is visible by emacs in the top node when I use M-x info command, but when I try to go to asymptote node, it complains "Info-find-file: Info file asymptote does not exist". The problem looks similar to info indexing (within and without emacs) although it is not quite the same. It seems that info command in emacs does not recognize the subdirectory, while the original info command does. Is it possible to force emacs behave in the same way?