I'm running a Mikrotik Cloud Hosted Router as an HVM DomU under Xen. How do I give it full control of the wifi card instead of my Dom0? The DomU needs to be able to associate and disassociate with networks, as well as host them, so NAT and bridging don't suit my circumstances.
You may use PCI passthrough to allow your HVM access the device directly.
Details about how to identify PCI BDF (the address of your wifi card in the PCI bus) and how to configure the domU are very much dependent of your Xen version and dom0 distribution.
Just as an example, I am using right now QubesOS, which is basically a Xen 4.6 installation with Fedora as dom0, and all network cards (both wired and wireless) are handled by a
sys-net VM, so there is no network running on dom0.