lock: add notes

Signed-off-by: Micky Ching <mickyching@gmail.com>
mm: add notes

Signed-off-by: Micky Ching <mickyching@gmail.com>
cache: add notes

Signed-off-by: Micky Ching <mickyching@gmail.com>
cache: add notes

Signed-off-by: Micky Ching <mickyching@gmail.com>
blkdev: add notes

Signed-off-by: Micky Ching <mickyching@gmail.com>
block: add notes

Signed-off-by: Micky Ching <mickyching@gmail.com>
sdio: add notes

Signed-off-by: Micky Ching <mickyching@gmail.com>