class BannerPage extends Page {

    public static $db = array(

    );

    public static $has_one = array(
        "LeftBanner" => "TextBanner",
        "RightBanner" => "TextBanner"
    );

    public function getCMSFields() {
        $fields = parent::getCMSFields();
        $fields->addFieldsToTab("Root.LeftBanner", $this->LeftBanner()->getCMSFields());
        $fields->addFieldsToTab("Root.RightBanner", $this->RightBanner()->getCMSFields());
        return $fields;
    }

}

class BannerPage_Controller extends Page_Controller {

}