Configure Atheros AR9285 wireless in Gentoo

I got the solution on Gentoo Forums. It turned out to be a mis-configured kernel.

Here is the kernel configuration that works (from the post that I linked to above):

[*] Networking support  --->
    -*-   Wireless  --->
        <*>   cfg80211 - wireless configuration API                                                                                                                  
        [*]     enable powersave by default
        [*]     cfg80211 wireless extensions compatibility
        [*]   Wireless extensions sysfs files
        <*>   Common routines for IEEE802.11 drivers
        <*>   Generic IEEE 802.11 Networking Stack (mac80211)
              Default rate control algorithm (Minstrel)  --->
        -*-   Enable LED triggers

Device Drivers  --->
    [*] Network device support  --->
        [*]   Wireless LAN  --->
            <*>   Atheros Wireless Cards  --->
                <*>   Atheros 802.11n wireless cards support