I am trying to install a Linux kernel (3.8.1) from source in a Fedora distribution.
The kernel is a vanilla one.
I follow the kernel's build instructions closely that is:

 make menuconfig
 make
 sudo make modules_install install
 sudo grub2-mkconfig -o /boot/grub2/grub.cfg

Everything in `/boot` seems fine.
I can see `System.map`, `initramfs`, and `vmlinuz` for the newly compiled kernel.
The `vmlinuz` link points to `vmlinuz-3.8.1`.
There are multiple other kernels installed including an Ubuntu one.
grub2 recognises all of them and I can boot to each one of them.

When I reboot I see all kernels as menu entries and choose 3.8.1.

Then I see this message:

 early console in decompress_kernel
 decompressing Linux... parsing ELF ... done
 Booting the kernel.
 [1.687084] systemd [1]:failed to mount /dev:no such device
 [1.687524] systemd [1]:failed to mount /dev:no such device

Solution:

All three posted responses provide the solution. CONFIG_DEVTMPFS was in fact causing the issue. I copied a working kernel's /boot/config-… into the root of the source tree as .config and executed the standard commands for building the kernel also shown above.


PS: Since I can only give one tick, it's fair to give it to the most concise answer providing the shortest time-to-solution. Thank you all.