docs(routing.md): add max parallel requests to router docs

docs/my-website/docs/routing.md

@@ -443,6 +443,35 @@ asyncio.run(router_acompletion())
 
 ## Basic Reliability
 
+### Max Parallel Requests (ASYNC)
+
+Used in semaphore for async requests on router. Limit the max concurrent calls made to a deployment. Useful in high-traffic scenarios. 
+
+If tpm/rpm is set, and no max parallel request limit given, we use the RPM or calculated RPM (tpm/1000/6) as the max parallel request limit. 
+
+
+```python
+from litellm import Router 
+
+model_list = [{
+	"model_name": "gpt-4",
+	"litellm_params": {
+		"model": "azure/gpt-4",
+		...
+		"max_parallel_requests": 10 # 👈 SET PER DEPLOYMENT
+	}
+}]
+
+### OR ### 
+
+router = Router(model_list=model_list, default_max_parallel_requests=20) # 👈 SET DEFAULT MAX PARALLEL REQUESTS 
+
+
+# deployment max parallel requests > default max parallel requests
+```
+
+[**See Code**](https://github.com/BerriAI/litellm/blob/a978f2d8813c04dad34802cb95e0a0e35a3324bc/litellm/utils.py#L5605)
+
 ### Timeouts 
 
 The timeout set in router is for the entire length of the call, and is passed down to the completion() call level as well.