There is a single Q-Channel for clock gating the GIC-600 Distributor. The Q-Channel interface denies access if the Distributor block is busy processing interrupts.
The Distributor also has a separate Q-Channel that enables power control for each configured ITS. The Q-Channel reads GITS_CTLR.Quiescent to check whether the ITS is fully disabled. If the Quiescent bit is set, the Q-Channel qacceptn_its signal is asserted, and the GIC guarantees that the bus to the relevant ITS is idle in both directions and that the ITS can be powered down.