On the Apple II series of computers, peripheral cards contend for bus mastership through a priority daisy-chain system. A peripheral card is only allowed to perform DMA if its DMA_IN line is at logic 1, indicating that no higher-priority cards are using the bus. When performing DMA, a card must set DMA_OUT to logic "0" in order to inhibit lower-priority cards from mastering the bus.
However, I have recently become aware of a different convention regarding the DMA_IN and DMA_OUT lines. Some ROM cards and Language Card-type RAM cards use the DMA_IN and DMA_OUT lines to arbitrate between multiple cards using the /INH feature. This can be seen in the Apple 050-0009-01 ROM card schematic, in which the DMA_OUT line is a logical AND between DMA_IN and the enable signal for the onboard ROMs.
I can understand this usage of the DMA_IN and DMA_OUT lines, but where can I see this usage of the DMA priority daisy chain discussed further?