In RHV-H you can upgrade and reinstall a Red Hat Virtualization Hypervisor host from an ISO image centrally stored on the Red Hat Virtualization Manager. Upgrading and reinstalling means that you are stopping and restarting the host. This can be either done manually by entering maintenance mode for the individual hosts or using a automated process of scheduling and applying updates to the cluster by setting hosts to maintenance mode in round-robin fashion (like e.g. with VMware Update Manager).
In RHEL Hypervisor hosts Patching is done via the normal patching processes via RHN or Satellite. Reboot can either be done manually or scheduled in round-robin fashion.