Update TensorRT documentation

docs/build/eps.md

@@ -144,6 +144,8 @@ See more information on the TensorRT Execution Provider [here](../execution-prov
 
 Dockerfile instructions are available [here](https://github.com/microsoft/onnxruntime/tree/main/dockerfiles#tensorrt)
 
+**Note** Building with `--use_tensorrt_oss_parser` with TensorRT 8.X requires additional flag --cmake_extra_defines onnxruntime_USE_FULL_PROTOBUF=ON
+
 ---
 
 ## NVIDIA Jetson TX1/TX2/Nano/Xavier/Orin

docs/execution-providers/TensorRT-ExecutionProvider.md

@@ -824,3 +824,7 @@ This example shows how to run the Faster R-CNN model on TensorRT execution provi
     ```
 
 Please see [this Notebook](https://github.com/microsoft/onnxruntime/blob/main/docs/python/notebooks/onnx-inference-byoc-gpu-cpu-aks.ipynb) for an example of running a model on GPU using ONNX Runtime through Azure Machine Learning Services.
+
+## Known Issues
+- TensorRT 8.6 built-in parser and TensorRT oss parser behaves differently. Namely built-in parser cannot recognize some custom plugin ops while OSS parser can. See [EfficientNMS_TRT missing attribute class_agnostic w/ TensorRT 8.6
+](https://github.com/microsoft/onnxruntime/issues/16121).