In my previous post I talk about CONFIG_SERIO_I8042 but I was wrong! Problem is that I can not disable mouse, which is consuming additional irq. I definitely would not use mouse, PS2 AT keyboard is enough, but I can not disable making of these drivers!
linux-2.6.19.2 on x86_32 arhcitecture, "make menuconfig" - how to disable mouse device to be built?

OK! - I will response for myself.;o(
Precompiled kernel 2.6.8-2-386 #1 coming with netsinst Debian 3.1 r4 have modules loaded mousedev, evdev and psmouse. According to this there are two interrupts aimed by i8042 1 and 12 (on my box).
When I'm removing psmouse - the secondary (12) irq is became free!
After I'm removed mousedev - the keyboard is working well.
After I'm removed evdev - the keyboard still working well.
Seem to me these modules I does not need at all!
But how to switch them off in kernel configuration?

Try removing or commenting out appropriate lines in /etc/modules.autoload.d/kernel-<version>.

Good idea!
One problem, I'd like to use kernel 2.6.19.2 (the newest one) than 2.6.8 which comes with Debian 3.1 r4 installer.
I'm trying about 10 times different configuration settings.
First what I realized I should check "Configure standard fetures (for small system)" in general setup. In this case menuconf allow me configure some more fields around Input drivers.
Now I does not check any kind of mouses but AT keyboard, libps2 and i8042 driver, but it does not help - i8042 driver aims two interrupts, event if psmouse and atkbd mosules are does not present!
I will try build a PS2 mouse module and load/unload to check what with second interrupt would happen!
One thing that I'm affraid that I machinate long part, and the problem reside in different place;o(

At last I've get it! - with help of the author of input modules - thanks.
Need to path kernel parameter called i8042.noaux - which disable to use AUX port for mices - in result it does not use irq 12.
Funny, I struggling the WEB for hours, when the answer was on my hard disk - in the kernel Documentation;D