/usr/lib/erlang/erts-5.10.4/doc is in erlang-doc 1:16.b.3-dfsg-1ubuntu2.2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/erlang/erts-5.10.4/../../../share/doc/erlang-doc/erts-5.10.4/doc
/usr/lib/erlang/erts-5.10.4/../../../share/doc/erlang-doc/erts-5.10.4/doc