g:dma controller integrated into devices themselves
https://www.pebblebay.com/direct-memory-access-embedded-systems/
Archived at: https://web.archive.org/web/20150108173450/https://www.pebblebay.com/direct-memory-access-embedded-systems/
Some peripheral devices have their own built-in DMA controller, meaning that they can 
take over the system bus and carry out DMA transfers without needing a separate system 
DMA controller. Devices that can take over the system bus are known as bus masters or 
devices that have bus mastering capabilities. Typical examples are disk controllers, 
Ethernet controllers, USB controllers, and video controllers. 
Usually the DMA controller built into these devices can only move data between the 
device itself and main memory – that is, it’s not intended to be used as 
a general system DMA controller.

g:dma controller integrated into devices themselves
https://softwareengineering.stackexchange.com/questions/272470/how-does-a-dma-controller-work

https://en.wikipedia.org/wiki/UDMA
https://en.wikipedia.org/wiki/Serial_ATA
https://en.wikipedia.org/wiki/M.2
https://en.wikipedia.org/wiki/U.2

P2PDMA
https://www.snia.org/sites/default/files/SDC/2018/presentations/Storage_Architecture/Bates_Stephen_Accelerating_Storage_with_NVM_Express_SSDs_and_P2PDMA.pdf