Unfortunately we do not support iSCSI explicitly in the PDK. You would need to follow standard instructions to enable iSCSI in the kernel and the PDK docs on rebuilding the kernel for the DPX2 platform. Thanks.
There is no documentation for your topic.
But at a high level the way to do this is to “tar” the RFS from the target and copy to the host. If you want to flash to another target
Move <PDK_install_dir>/drive-t186ref-linux/targetfs to somewhere else
Untar the rfs you copied from the target into this <PDK_install_dir>/drive-t186ref-linux/targetfs directory