...I did not see where you defined your "bootargs" variable, and the correct boot comand for using a ramdisk has two arguments instead of one.

Sorry I'm confused, why these settings won't be enough ?

U-Boot> printenv

bootdelay=3 baudrate=115200 ethaddr=00:02:a5:6e:3f:fd filesize=3638c0 fileaddr=21140000 netmask=255.255.255.0 ipaddr=192.168.0.184 serverip=192.168.0.11 bootargs=root=/dev/ram rw initrd=0x21100000,6000000 ramdisk_size=15360 console=ttyS0,115200 mem=32M stdin=serial stdout=serial stderr=serial

TIA