How to set in kernel linux parameter list reboot=w?

[tomek244]

Hi
I need to make in software that reboot linux command do warm reset by default instead of hard/cold reboot.
I found in kernel sources that I need to patch this piece of code linux-socfpga/kernel/reboot.c:

$this->bbcode_second_pass_code('', '#if defined(CONFIG_ARM) || defined(CONFIG_UNICORE32)
#define DEFAULT_REBOOT_MODE = REBOOT_HARD')
Instead of REBOOT_HARD I need to make patch and add REBOOT_WARM.
However I go to know that I can also place in some boot kernel parameter list this line:
$this->bbcode_second_pass_code('', 'reboot=w')
But the problem is that I cannot find linux boot kernel parameter list.
Could anybody help?
I am using:
https://github.com/altera-opensource/u- ... a_v2017.09
and
https://github.com/altera-opensource/linux-socfpga
and hw: stratix-10 for example in uboot the directory is: mach-socfgfpa and drivers with end _s10.c