Add documentation on the initializtion process of DreamOs

docs/kernel/Initialization.md

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+#  Kernel Initialization
+
+## Loading the kernel
+
+The kernel is loaded by grub2, using the multibtoo2 specifications.
+
+The tags that are enabled at boot are:
+
+* Framebuffer
+
+Although it is optional, in the mid term, support for legacy VGA driver will be dropped.
+
+The header is defined in the `src/asm/multiboot_header.s`
+
+Additional tags maybe added in the future (although the long term plan is to replace grub with limine)
+
+We let the bootloader decide for the framebuffer configuration (that is: Width, Height, Depth)
+
+## Booting process (Early boot)
+
+As soon as multiboot pass the control to the kernel loader, the early boot stages are done mostly in the `src/asm/boot.s` file. That will do the following steps:
+
+* Set up paging and map the kernel in the higher half
+* Pre parse the multiboot data passed by grub, preparing the data that will be needed by the kernel.
+* Enable PAE
+* Map the first 4 megabyte of the Framebuffer
+* Jump to the kernel in  the higher half
+
+## Booting Process (Late Boot)
+
+Once the setup in the early boot process is done,  the kernel is fully loaded in the higher half, and we can proceed with the rest of the Initialization
+
+The sequence of component that are intialized (refer to `src/main.c`):
+
+* Qemu debug (the main output for now)
+* IDT
+* Basic System:
+    - Parse the multiboot information received from the bootloader.
+    - Parse the mmap and initialize the physical memory manager, marking the pmm areas as busy.
+    - Initialize the physical mermoy manager, marking the area in the mmap as already taken.
+    - Validate and parse the SDT tables
+    - This section needs to be reviewed and check if all the steps are required
+* Load the PSF font from memory
+* Finish mapping the Framebuffer (there is a potential bug here, need to chek what i do while mapping it)
+* Set the Higher Half direct map
+* Initialize the kernel VMM
+* Initialize the kernel heap
+* Initialize the apic
+* Initialize the keyboard
+* Initialize and load the TSS
+* Calibrate the apic timer
+* Initialize the VFS layer (although not really used)
+* Initialize the scheduler
+* Finally start the timer, that it will make the scheulder start working and picking tasks when present in the queue, or run the idle tasks when the queue is empty.
+
+At this point the startup is completed and the kernel starts its infinite loop.