I already added the phylib supporting and ethtool carrier detection in fec.c driver. Here is my git tree containing those patches:
http://kernel.ubuntu.com/git?p=roc/ubuntu-lucid.git;a=shortlog;h=refs/heads/fec;pg=0

Please find my kernel package here for testing:
http://people.canonical.com/~roc/kernel/fec/

Booting with networking cable plugged in:
---
roc@babbage:~$ uname -a
Linux babbage 2.6.31-605-imx51 #10~fec+phylib Wed Mar 24 16:19:20 CST 2010 armv7l GNU/Linux
roc@babbage:~$ dmesg | grep eth0
eth0: Freescale FEC PHY driver [SMSC LAN8700] (mii_bus:phy_addr=0:00, irq=-1)
eth0: no IPv6 routers present
roc@babbage:~$ dmesg | tail
type=1505 audit(1269420454.019:10): operation="profile_load" pid=527 name=/usr/bin/evince-thumbnailer
type=1505 audit(1269420454.109:11): operation="profile_load" pid=540 name=/usr/lib/cups/backend/cups-pdf
PHY: 0:00 - Link is Up - 100/Full
lp: driver loaded but no devices found
ppdev: user-space parallel port driver
DMFC high resolution has set, will not change
mxc_ipu mxc_ipu: Channel already disabled 9
mxc_ipu mxc_ipu: Channel already uninitialized 9
DMFC high resolution has set, will not change
eth0: no IPv6 routers present
roc@babbage:~$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:04:9f:00:e8:c8  
          inet addr:192.168.0.102  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::204:9fff:fe00:e8c8/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:37 errors:0 dropped:0 overruns:0 frame:0
          TX packets:29 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:9868 (9.8 KB)  TX bytes:4661 (4.6 KB)
          Base address:0xe000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:4 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:240 (240.0 B)  TX bytes:240 (240.0 B)

roc@babbage:~$ nm-tool 

NetworkManager Tool

State: connected

- Device: eth0  [Auto eth0] ----------------------------------------------------
  Type:              Wired
  Driver:            fec
  State:             connected
  Default:           yes
  HW Address:        00:04:9F:00:E8:C8

  Capabilities:
    Carrier Detect:  yes
    Speed:           100 Mb/s

  Wired Properties
    Carrier:         on

  IPv4 Settings:
    Address:         192.168.0.102
    Prefix:          24 (255.255.255.0)
    Gateway:         192.168.0.1

    DNS:             202.109.14.5
    DNS:             124.74.213.68
----

Remove the cable:
---
roc@babbage:~$ dmesg | tail
type=1505 audit(1269420454.109:11): operation="profile_load" pid=540 name=/usr/lib/cups/backend/cups-pdf
PHY: 0:00 - Link is Up - 100/Full
lp: driver loaded but no devices found
ppdev: user-space parallel port driver
DMFC high resolution has set, will not change
mxc_ipu mxc_ipu: Channel already disabled 9
mxc_ipu mxc_ipu: Channel already uninitialized 9
DMFC high resolution has set, will not change
eth0: no IPv6 routers present
PHY: 0:00 - Link is Down
roc@babbage:~$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:04:9f:00:e8:c8  
          inet6 addr: fe80::204:9fff:fe00:e8c8/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:85 errors:0 dropped:0 overruns:0 frame:0
          TX packets:29 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:25848 (25.8 KB)  TX bytes:4661 (4.6 KB)
          Base address:0xe000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:4 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:240 (240.0 B)  TX bytes:240 (240.0 B)
---

Insert cable again:
---
roc@babbage:~$ dmesg | tail
PHY: 0:00 - Link is Up - 100/Full
lp: driver loaded but no devices found
ppdev: user-space parallel port driver
DMFC high resolution has set, will not change
mxc_ipu mxc_ipu: Channel already disabled 9
mxc_ipu mxc_ipu: Channel already uninitialized 9
DMFC high resolution has set, will not change
eth0: no IPv6 routers present
PHY: 0:00 - Link is Down
PHY: 0:00 - Link is Up - 100/Full
roc@babbage:~$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:04:9f:00:e8:c8  
          inet addr:192.168.0.102  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::204:9fff:fe00:e8c8/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:108 errors:0 dropped:0 overruns:0 frame:0
          TX packets:56 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:31139 (31.1 KB)  TX bytes:8859 (8.8 KB)
          Base address:0xe000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:4 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:240 (240.0 B)  TX bytes:240 (240.0 B)
---

We can also see such change in the GUI.

-Bryan