mach-virt-serial-usb.xml

<domain type='qemu'>
  <name>guest</name>
  <uuid>1ccfd97d-5eb4-478a-bbe6-88d254c16db7</uuid>
  <memory unit='KiB'>524288</memory>
  <vcpu placement='static'>1</vcpu>
  <os>
    <type arch='aarch64' machine='virt'>hvm</type>
  </os>
  <devices>
    <emulator>/usr/bin/qemu-system-aarch64</emulator>
    <controller type='usb' model='qemu-xhci'/>
    <!-- This should be assigned a USB address. You'll not be able to find it
         in the file generated by qemuxml2xmltest due to limitations in the
         test suite, but it will be there when actually running libvirt;
         moreover, the USB address will be present in the .args file -->
    <serial type='pty'>
      <target type='usb-serial'/>
    </serial>
    <memballoon model='none'/>
  </devices>
</domain>