qemu manpage: describe arguments of usbdevice option

diff -u -d -p -r1.175 qemu-doc.texi
@@ -492,6 +492,28 @@ Enable the USB driver (will be the defau
 
 @item -usbdevice @var{devname}
 Add the USB device @var{devname}. @xref{usb_devices}.
+
+@table @code
+
+@item mouse
+Virtual Mouse. This will override the PS/2 mouse emulation when activated.
+
+@item tablet
+Pointer device that uses absolute coordinates (like a touchscreen). This
+means qemu is able to report the mouse position without having to grab the
+mouse. Also overrides the PS/2 mouse emulation when activated.
+
+@item disk:file
+Mass storage device based on file
+
+@item host:bus.addr
+Pass through the host device identified by bus.addr (Linux only).
+
+@item host:vendor_id:product_id
+Pass through the host device identified by vendor_id:product_id (Linux only).
+
+@end table
+
 @end table
 
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