default or selected kernelversion does not have config value CONFIG_SERIAL_SIRFSOC_CONSOLE.
Result is shown for kernelversion 6.9.9

Support for console on SiRF SoC serial port

configname: CONFIG_SERIAL_SIRFSOC_CONSOLE

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>Serial drivers
└─>Support for console on SiRF SoC serial port
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Even if you say Y here, the currently visible virtual console
(/dev/tty0) will still be used as the system console by default, but
you can alter that using a kernel command line option such as
"console=ttySiRFx". (Try "man bootparam" or see the documentation of
your boot loader about how to pass options to the kernel at
boot time.)