Making MKDIR_P Directory Rule like Emacs using ${trgdir}

In the Emacs documentation makefile, this makes the directory
where the resulting emacs.info file is placed

MKDIR_P = @MKDIR_P@
${buildinfodir}:
	${MKDIR_P} $@

In my case, I want the info file to exist in the build directory
target stored in trgdir.  What recipe shall I use to make
trgdir if it does not exist?

${trgdir}:
	${MKDIR_P} $@