[Doc] format lora related docs for the user's end (#1009)

Signed-off-by: AndyZhou952 <jzhoubc@connect.ust.hk>
Signed-off-by: Andy Zhou <46011930+AndyZhou952@users.noreply.github.com>

docs/user_guide/examples/online_serving/text_to_image.md

@@ -61,6 +61,59 @@ python gradio_demo.py
 # Visit http://localhost:7860
 ```
 
+## LoRA
+
+This example supports Peft-compatible LoRA (Low-Rank Adaptation) adapters for diffusion models. The LoRA adapter path must be readable on the **server** machine (usually a local path or a mounted directory).
+
+### Using Python Client with LoRA
+
+```bash
+python openai_chat_client.py \
+  --prompt "A piece of cheesecake" \
+  --lora-path /path/to/lora_adapter \
+  --lora-name my_lora \
+  --lora-scale 1.0 \
+  --output output.png
+```
+
+### Using curl with LoRA (Images API)
+
+The `/v1/images/generations` endpoint supports a `lora` field in the request body:
+
+```bash
+curl -X POST http://localhost:8091/v1/images/generations \
+  -H "Content-Type: application/json" \
+  -d '{
+    "prompt": "A piece of cheesecake",
+    "size": "1024x1024",
+    "seed": 42,
+    "lora": {
+      "name": "my_lora",
+      "local_path": "/path/to/lora_adapter",
+      "scale": 1.0
+    }
+  }' | jq -r '.data[0].b64_json' | base64 -d > output.png
+```
+
+### LoRA Parameters
+
+| Parameter     | Type   | Description                                                      |
+| ------------- | ------ | ---------------------------------------------------------------- |
+| `name`        | str    | LoRA adapter name (optional, defaults to path stem)              |
+| `local_path`  | str    | Server-local path to LoRA adapter folder (PEFT format, required) |
+| `scale`       | float  | LoRA scale factor (default: 1.0)                                 |
+| `int_id`     | int    | LoRA integer ID for caching (optional, derived from path if not provided) |
+
+### LoRA Adapter Format
+
+LoRA adapters must be in PEFT (Parameter-Efficient Fine-Tuning) format. A typical LoRA adapter directory structure:
+
+```
+lora_adapter/
+├── adapter_config.json
+└── adapter_model.safetensors
+```
+
 ## Request Format
 
 ### Simple Text Generation