CONFIG_SOC_IMX50 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

i.MX50 support

modulename: mach-imx50.ko

configname: CONFIG_SOC_IMX50

Linux Kernel Configuration
└─>Freescale i.MX family
└─>i.MX50 support
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
This enables support for Freescale i.MX50 processor.

source code:
arch/arm/mach-imx/mach-imx50.c
selects
CONFIG_SOC_IMX5
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is selected by
CONFIG_PINCTRL_IMX50
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