[Deepseek V3.2] Support Overlap Spec + NSA (#15307)

Co-authored-by: Brayden Zhong <b8zhong@users.noreply.github.com>

docs/basic_usage/deepseek_v32.md

@@ -77,6 +77,10 @@ python -m sglang.launch_server --model deepseek-ai/DeepSeek-V3.2-Exp --tp 8 --sp
 - The best configuration for `--speculative-num-steps`, `--speculative-eagle-topk` and `--speculative-num-draft-tokens` can be searched with [bench_speculative.py](https://github.com/sgl-project/sglang/blob/main/scripts/playground/bench_speculative.py) script for given batch size. The minimum configuration is `--speculative-num-steps 1 --speculative-eagle-topk 1 --speculative-num-draft-tokens 2`, which can achieve speedup for larger batch sizes.
 - The default value of  `--max-running-requests` is set to `48` for MTP. For larger batch sizes, this value should be increased beyond the default value.
 
+```{tip}
+To enable the experimental overlap scheduler for EAGLE speculative decoding, set the environment variable `SGLANG_ENABLE_SPEC_V2=1`. This can improve performance by enabling overlap scheduling between draft and verification stages.
+```
+
 
 ## Function Calling and Reasoning Parser
 The usage of function calling and reasoning parser is the same as DeepSeek V3.1. Please refer to [Reasoning Parser](https://docs.sglang.io/advanced_features/separate_reasoning.html) and [Tool Parser](https://docs.sglang.io/advanced_features/tool_parser.html) documents.