o hotplug slots add
  When the hot-added PCI device is p2p bridge, acpiphp calls
  find_p2p_bridge() to add hotplug slots.

o hotplug slots remove
  When the hot-removing PCI device is p2p bridge, acpiphp
  calls cleanup_p2p_bridge() to remove hotplug slots.

o notify handler exchange
  When the p2p bridge is added, acpiphp changes the notify
  hanlder.
  If no bridge device is inserted into the hotpluggable PCI
  slot, acpiphp installs the notify handler for function.
  After the p2p bridge hot-add, acpiphp has to install the
  notify handler for bridge. Because, the role of the
  handlers are not same. The hot-remove case is ditto.
Signed-off-by: NMUNEDA Takahiro <muneda.takahiro@jp.fujitsu.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>