Save as otherwise provided under this Act, no person shall establish or maintain any institution for persons with disabilities except in accordance with a certificate of registration issued in this behalf by the competent authority:
     Provided that an institution for care of mentally ill persons, which holds a valid licence under section 8 of the Mental Health Act, 1987 (14 of 1987) or any other Act for the time being in force, shall not be required to be registered under this Act.