CONFIG_UCC_SLOW is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

UCC Slow Protocols Support

modulename: ucc_slow.ko

configname: CONFIG_UCC_SLOW

Linux Kernel Configuration
└─>QE Options
└─>UCC Slow Protocols Support
In linux kernel since version 2.6.19 (release Date: 2006-11-29)  
This option provides qe_lib support to UCC slow
protocols: UART, BISYNC, QMC

source code:
arch/powerpc/sysdev/qe_lib/ucc_slow.c
selects
CONFIG_UCC


is depended by
CONFIG_UCC_FAST