drm_dp_mst_topology_get_mstb_validated
mstb = drm_dp_mst_topology_get_mstb_validated(mgr, port->parent);
mstb = drm_dp_mst_topology_get_mstb_validated(mgr, port->parent);
mstb = drm_dp_mst_topology_get_mstb_validated(mgr, port->parent);
mstb = drm_dp_mst_topology_get_mstb_validated(mgr, port->parent);