I should thank you :-) You finally motivated me to start a wiki page for this stuff: http://www.coreboot.org/Exynos5

You will need a payload. If you wish to try a simple pseudo payload, the "hello world" example for libpayload would be a good start: http://www.coreboot.org/Libpayload .

The term "payload" refers to the code which runs after coreboot, so you will need one. Unlike pmon2000, u-boot, uefi, etc, coreboot does not attempt to function as an OS in any capacity. It does not include an interactive console or a network server. It is intended to perform very basic hardware initialization only. Everything else is the responsibility of the payload.

The "payload" may be a Linux kernel if you can fit it on the ROM. As Vladimir pointed out, this is only 512KB. If you have a very small kernel then you may simply set it as the payload.