CONFIG_ALPHA_MIATA is not available for thedefaultarchitecture x86.
Result is shown for architecture alpha

Miata

modulename: sys_miata.ko

configname: CONFIG_ALPHA_MIATA

Alpha system type
└─>Miata
In linux kernel since version 2.6.12  
The Digital PersonalWorkStation (PWS 433a, 433au, 500a, 500au, 600a,
or 600au).

source code:
arch/alpha/kernel/