Change to usb(4) to include usb/serial.
This is actually from Gorka but I think he forgot to
send the man (according to diff to sources).

Notes:
Fri May 29 13:32:51 EDT 2009 geoff
    already done; gorka had sent his updated manual page,
    and our updated page should already be on sources.


Reference: /n/sources/patch/sorry/usbserialman
Date: Fri May 29 18:03:32 CES 2009
Signed-off-by: nemo@lsub.org
Reviewed-by: geoff

--- /sys/man/4/usb	Fri May 29 18:01:59 2009
+++ /sys/man/4/usb	Fri May 29 18:01:56 2009
@@ -6,7 +6,6 @@
 kb,
 print,
 probe,
-serial,
 usbfat:
 \- Universal Serial Bus device drivers
 .SH SYNOPSIS
@@ -218,6 +217,28 @@
 The file is also bound at
 .B /dev/lp
 as is customary.
+.SS Serial
+.I Serial
+provides provides a file system (usually seen at /dev) that includes
+one directory per serial port, named
+.B eiaUN .
+In this directory there are two files,
+.B eiaUN/data
+similar to the file eiaN in
+.IR eia (3)
+and
+.B eiaUN/ctl .
+The control file admits writes
+.B eiaUN/ctl
+in the same format as
+.B eiaNctl
+in
+.IR eia (3).
+Reading from this file gives the parameters of the serial port in the same format as
+.B eiaNstatus
+in
+.IR eia (3).
+Options are similar to those of disk. 
 .SS Ethernet adapters
 .I Ether
 provides a file interface similar to that of
@@ -231,35 +252,6 @@
 When started manually, the file interface is mounted at
 .B /net
 as is customary.
-.
-.SS Serial ports
-.I Serial
-provides a file system (usually mounted at
-.BR /dev )
-that includes one directory per USB serial port, named
-.BI eiaU N.
-In this directory there are two files,
-.BI eiaU N /data ,
-similar to
-.BI eia N
-in
-.IR eia (3),
-and
-.BI eiaU N /ctl .
-.I Ctl
-admits writes in the same format as
-.BI eia N ctl
-in
-.IR eia (3).
-Reading from
-.I ctl
-gives the serial port's settings in the same format as
-.BI eia N status
-in
-.IR eia (3).
-Options are similar to those of
-.IR disk .
-.
 .SS Audio devices
 .I Usbaudio
 configures and manages a USB audio device.
@@ -363,7 +355,6 @@
 .SH SOURCE
 .B /sys/src/cmd/usb
 .SH "SEE ALSO"
-.IR eia (3),
 .IR kbin (3),
 .IR mouse (3),
 .IR sd (3),
@@ -376,11 +367,8 @@
 ATA storage devices are not supported.
 Both the Ethernet and printer drivers have not
 been tested and it is likely they will fail.
-The serial driver works only for the Prolific chip, and control of the
-.B dcd
-and
-.B dsr
-signals and some of the extra features are unimplemented.
+The serial driver works only for the Prolific chip and the dcd and dsr
+control and some of the extra features are unimplemented.
 .PP
 Not heavily exercised yet.
 The entire set of drivers is new and therefore potentially unreliable.