If you want to add System z zFCP drives to a Debian GNU/Linux system, you first need to make the HBA known to the system. For this you add an (initially empty) file with the (lowercase) device ID of the zFCP HBA to /etc/sysconfig/hardware. There should already be files for the ECKD/FBA disks and the network adapters.
Then you need to list the drives to initialize by placing the following array in it with a list of WWPN:LUN, seperated by spaces within the parentheses:
Please keep in mind that the WWPN and LUN need to be specified in hex and again entirely in lower case. This will cause hwup ccw 0.0.4000 (with 4000 being the CHPID) to instruct the HBA to add the drive after setting it online. Then you should regenerate your initrd, so that it happens on-boot, by running update-initramfs -u -k all.
With current kernels the available WWPNs should be probed and listed in /sys/bus/ccw/devices/0.0.4000 without further intervention after the HBA is initialized.
Sadly there's no way to set up a zFCP disk in debian-installer.