I have attempted to selectively install linux-image-4.0.0-2-kirkwood from unstable on QNAP-212P.
This resulted in the following:
## Booting image at 00800000 ...
Image Name: kernel 4.0.0-2-kirkwood
Created: 2015-05-28 18:37:03 UTC
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 2066352 Bytes = 2 MB
Load Address: 00008000
Entry Point: 00008000
Verifying Checksum ... OK
OK
Starting kernel ...
Uncompressing Linux... done, booting the kernel.
Error: unrecognized/unsupported machine ID (r1 = 0x0000085b).
Available machine support:
ID (hex) NAME
ffffffff Generic DT based system
ffffffff Marvell Kirkwood (Flattened Device Tree)
Please check your kernel config and/or bootloader.
I don't really understand how Debian handles the passing of dtb files (only legacy machine id? appends them to the kernel? points to the /boot/ with dtbs?) or how to fix it, but in any case be warned that if you update now, you may end up in the same situation.
Best regards,
Jan