[docs][ci skip] Add docs on SHA3 mixin

docs/Generators/SHA3.rst

@@ -68,3 +68,18 @@ on which available execution unit they should be run. Once
 the message is fully hashed, the hash is written to memory
 with a simple state machine.
 
+
+Using a SHA3 Accelerator
+------------------------
+Since the SHA3 accelerator is designed as a RoCC accelerator,
+it can be mised into a Rocket or BOOM core by overriding the
+BuildRoCC key. The configuration mixin is defined in the SHA3
+generator. An example configuration highlighting the use of
+this mixin is shown here:
+
+.. literalinclude:: ../../generators/example/src/main/scala/RocketConfigs.scala
+   :language: scala
+   :start-after: DOC include start: Sha3Rocket
+   :end-before: DOC include end: Sha3Rocket
+
+

generators/example/src/main/scala/RocketConfigs.scala

@@ -104,6 +104,7 @@ class GB1MemoryRocketConfig extends Config(
   new freechips.rocketchip.subsystem.WithNBigCores(1) ++
   new freechips.rocketchip.system.BaseConfig)
 
+// DOC include start: Sha3Rocket
 class Sha3RocketConfig extends Config(
   new WithTop ++
   new WithBootROM ++
@@ -111,6 +112,7 @@ class Sha3RocketConfig extends Config(
   new sha3.WithSha3Accel ++                                // add SHA3 rocc accelerator
   new freechips.rocketchip.subsystem.WithNBigCores(1) ++
   new freechips.rocketchip.system.BaseConfig)
+// DOC include end: Sha3Rocket
 
 // DOC include start: InitZeroRocketConfig
 class InitZeroRocketConfig extends Config(