Writing a FreeBSD kernel module that handles arbitrary interrupt and output to device

I would like to write a FreeBSD kernel module that could accept some arbitrary interrupts and upon receiving these interrupt, output some data to an arbitrary device. Currently, I'm facing several issues:

1. How would I acquire interrupts through a specific IRQ? On Linux there is the request_irq() call but it seems there's no similar API for FreeBSD... Say, I want to be able to detect all the keyboard interrupt through my kernel module (the keyboard is on irq1), how would I do that? (On Linux it is possible through calling free_irq(1, NULL) and request_irq(1, ...), correct me if I'm wrong though).

2. Is it possible at all to write to a device file under /dev through a kernel module? I've read the question Example for reading text files in FreeBSD kernel module; following this example I was able to do read/write on regular files, but not a device file under /dev (the "device" was a pseudo "echo device", the classical one used in char device examples). I was able to open the file though.
   I do understand that it is considered as a bad practice to do file I/O's in kernel, but I could not think any other way... If anyone has a better solution please tell me. (i.e. write to a device through its device_t node?)

The reason I was doing this in a kernel is that I really need all interrupts to be hit, and running it in the user space has the risk of missing interrupts due to kernel threads preempting user threads (the interrupts could come very frequent).

I would also appreciate if anyone could provide me with some other ideas on how to implement this program (basically, the idea is a kernel module that could do the job of a microcontroller...)