Menu::getRootline() 

\nn\t3::Menu()->getRootline($rootPid = NULL, $config = []); 

Returns a simple array with the rootline to the current page. Can be used for BreadCrumb navigations

// get rootline for current page ID (pid)
\nn\t3::Menu()->getRootline();

// get rootline for page 123
\nn\t3::Menu()->getRootline( 123 );

There is also a ViewHelper for this:

{nnt3:menu.rootline(pageUid:123, ...)}

public function getRootline( $rootPid = null, $config = [] )
{
	$config['type'] = 'rootline';
	return $this->get( $rootPid, $config )['children'];
}