If the certificate of incorporation or action by the board of directors pursuant to Section 10A-2A-6.02 authorizes dividing the stock into classes or series, the certificate of incorporation may also authorize the election of all or a specified number of directors by the holders of one or more authorized classes or series of stock. A class or series (or multiple classes or series) of stock entitled to elect one or more directors is a separate voting group for purposes of the election of directors.