Red Hat OpenStack Platform is only supported for use with the
libvirt driver (using KVM as the hypervisor on Compute nodes).
Ironic has been fully supported since the release of Red Hat OpenStack Platform 7 (Kilo). Ironic allows you to provision bare-metal machines using common technologies (such as PXE boot and IPMI) to cover a wide range of hardware while supporting pluggable drivers to allow the addition of vendor-specific functionality.
Red Hat does not provide support for other Compute virtualization drivers such as the deprecated VMware "direct-to-ESX" hypervisor, and non-KVM libvirt hypervisors.