<fontconfig>

       faces with STIX Math symbols -->

  <alias binding="same">

    <family>STIX Math</family>

    <accept>

      <family>STIX</family>

    </accept>

  </alias>

  <alias binding="same">

    <family>STIX</family>

    <accept>

      <family>STIX Math</family>

    </accept>

  </alias>

</fontconfig>