I see, we have a default src_unpack and a default src_compile but a default src_install is still
missing. Here is my suggestion (taken and modified from bug 33544):

src_install() {
	if [ -f Makefile -o -f GNUmakefile -o -f makefile ]; then
		emake DESTDIR=${D} install || die "emake install failed"
		[[ -n ${DOCS} ]] && dodoc ${DOCS}
	else
		einstall || die "einstall failed"
		[[ -n ${DOCS} ]] && dodoc ${DOCS}
	fi
}

Any comments?