Finally managed to get the Raspberry Pi2 (armv7) to boot Kernel 4.0, by re-creating the kernel config from scratch, with # make bcm2709_defconfig

Fedora release 21 (Twenty One)
Kernel 4.0.0-v7 on an armv7l (ttyAMA0)
............
]# uname -a
Linux rgpi2 4.0.0-v7 #1 SMP PREEMPT Wed Apr 15 17:12:00 PDT 2015 armv7l armv7l armv7l GNU/Linux

The ‘classic’ Pi had been able to utilise the imported config from 3.19.3, but – for some reason – the Pi 2 had not.

Now I will try to remove the kernel ‘debug’ settings, and see if it still boots!

Robert Gadsdon.  April 15, 2015.