\input luaotfload.sty
%% lookup font by name (involving database)
\font\first=name:iwonaregular at 42pt
%% lookup font by file name (kpse)
\font\second=file:antpoltltsemiexpd-bolditalic.otf at 42pt
%% lookup font by name, with style in slash notation
\font\third={name:Antykwa torunska/I} at 42pt

{\first   foo \endgraf}
{\second  bar \endgraf}
{\third   baz \endgraf}

\bye

