docs: Move sections around in pci-addresses.rst

The section about VFIO devices is kept separate from the rest
because it's less about domain XML and guest OS disagreeing on the
PCI address of a device, and more about which of the two PCI
addresses in the domain XML is even relevant to the guest OS.

The section on zPCI addresses, on the other hand, falls squarely
in the "more complex cases" category, so it should live in the
corresponding section.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>

docs/pci-addresses.rst

@@ -158,36 +158,8 @@ Once again, while the PCI addresses seen in the domain XML and those
 seen by the guest OS do not match, the relationships between the
 various devices are preserved.
 
-
-Device assignment
-=================
-
-When using VFIO to assign host devices to a guest, an additional
-caveat to keep in mind that the guest OS will base its decisions upon
-the *target address* (guest side) rather than the *source address*
-(host side).
-
-For example, the domain XML snippet
-
-::
-
-  <hostdev mode='subsystem' type='pci' managed='yes'>
-    <driver name='vfio'/>
-    <source>
-      <address domain='0x0001' bus='0x08' slot='0x00' function='0x0'/>
-    </source>
-    <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
-  </hostdev>
-
-will result in the device showing up as ``0000:00:01.0`` in the
-guest OS rather than as ``0001:08:00.1``, which is the address of the
-device on the host.
-
-Of course, all the rules and behaviors described above still apply.
-
-
 zPCI addresses
-==============
+--------------
 
 For s390x machines, PCI addresses are handled yet differently. No
 topology information is relayed in the PCI addresses; instead, the
@@ -252,3 +224,30 @@ will yield the following result in a Linux guest:
 ::
 
   0007:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device
+
+
+Device assignment
+=================
+
+When using VFIO to assign host devices to a guest, an additional
+caveat to keep in mind that the guest OS will base its decisions upon
+the *target address* (guest side) rather than the *source address*
+(host side).
+
+For example, the domain XML snippet
+
+::
+
+  <hostdev mode='subsystem' type='pci' managed='yes'>
+    <driver name='vfio'/>
+    <source>
+      <address domain='0x0001' bus='0x08' slot='0x00' function='0x0'/>
+    </source>
+    <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
+  </hostdev>
+
+will result in the device showing up as ``0000:00:01.0`` in the
+guest OS rather than as ``0001:08:00.1``, which is the address of the
+device on the host.
+
+Of course, all the rules and behaviors described above still apply.