SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
This may seem like a no-op change, however it shrinks down the Kernel by a bit:
.text -432
.unmap_after_init -60
.data -480
.debug_info -673
.debug_aranges 8
.debug_ranges -232
.debug_line -558
.debug_str -308
.debug_frame -40
With '= default', the compiler can do more inlining, hence the savings.
I intentionally omitted some opportunities for '= default', because they
would increase the Kernel size.
Such device is not an IRQHandler by itself, but actually a controller of
many IRQ or MSI devices. The purpose of this class is to manage multiple
sources of interrupts.
For example, a generic ISA IDE controller controls 2 IRQ sources - 14
and 15. So, when we initialize the IDE controller, it will initialize
two IDE channels (also known as PATAChannels) to utilize IRQ 14 and 15,
respectively. NVMe with MSI-X support can theoretically handle up to
2048 interrupts.
