add_action('init', 'infinitum_ninzio_enable_custom_font_format');
function infinitum_ninzio_enable_custom_font_format() {
    add_filter('upload_mimes', 'infinitum_ninzio_add_custom_upload_mimes');
    function infinitum_ninzio_add_custom_upload_mimes($existing_mimes) {
        $existing_mimes['otf'] = 'application/x-font-otf';
        $existing_mimes['woff'] = 'application/x-font-woff';
        $existing_mimes['ttf'] = 'application/x-font-ttf';
        $existing_mimes['svg'] = 'image/svg+xml';
        $existing_mimes['eot'] = 'application/vnd.ms-fontobject';
        return $existing_mimes;
    }

}