[llvm-mca][docs] Add notes about cycle and resource callbacks. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337225 91177308-0d34-0410-b5e6-96231b3b80d8

docs/CommandGuide/llvm-mca.rst

@@ -273,6 +273,14 @@ describes the state of an instruction (e.g., Ready, Dispatched, Executed,
 etc.).  The latter describes a stall hazard (e.g., load stall, store stall,
 scheduler stall, etc.).
 
+In addition to the instruction and stall events.  A listener can also
+subscribe to cycle events (``onCycleStart``, ``onCycleEnd``).  These events
+occur before and after a simulated clock cycle is executed, respectively.
+
+Listeners can also be notified of various resource states within the stages
+of a pipeline, such as resource availability, reservation, and reclaim:
+(``onResourceAvailability``, ``onReservedBuffers``, ``onReleasedBuffers``).
+
 Creating a Custom View
 """"""""""""""""""""""
 To create a  custom view, the user must first inherit from the ``View`` class