docs: documented the Programmable Interval Timer (PIT)

.wiki/Kernel-documentation.md

@@ -20,6 +20,7 @@ The single parts of the kernel are initialized in the following order:
     - **[PIC] Programmable Interrupt Controller**
   - **Paging**
   - **Kernel Heap**
+  - **Graphics Renderer**
   - **Scheduler**
 
 ## Interrupt handling
@@ -382,6 +383,18 @@ Returns the width of the framebuffer.
 #### `graphics_renderer_get_height()` - function (uint32_t)
 Returns the height of the framebuffer.
 
+### time/pit.h
+#### `PIT_CHANNEL_0_PORT` - macro
+The IO port, where channel 0 of the PIT (which is capable of firing IRQs) can be configured.
+
+#### `PIT_DIVISOR` - macro
+The standard divisor nox_os loads into channel 0 of the PIT.
+`32768` fires an interrupt every `~27ms`, what is perfect for preemptive multithreading.
+
+#### `pit_set_divisor(divisor)` - function (void)
+Loads **_divisor_** into channel 0 of the PIT.
+If **_divisor_** is smaller than 100, it will be set to 100.
+
 ## mm
 
 ### heap.h