[Doc] Reorganize user guide (#18661)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

docs/configuration/serve_args.md

@@ -0,0 +1,38 @@
+---
+title: Server Arguments
+---
+[](){ #serve-args }
+
+The `vllm serve` command is used to launch the OpenAI-compatible server.
+
+## CLI Arguments
+
+The `vllm serve` command is used to launch the OpenAI-compatible server.
+To see the available CLI arguments, run `vllm serve --help`!
+
+## Configuration file
+
+You can load CLI arguments via a [YAML](https://yaml.org/) config file.
+The argument names must be the long form of those outlined [above][serve-args].
+
+For example:
+
+```yaml
+# config.yaml
+
+model: meta-llama/Llama-3.1-8B-Instruct
+host: "127.0.0.1"
+port: 6379
+uvicorn-log-level: "info"
+```
+
+To use the above config file:
+
+```bash
+vllm serve --config config.yaml
+```
+
+!!! note
+    In case an argument is supplied simultaneously using command line and the config file, the value from the command line will take precedence.
+    The order of priorities is `command line > config file values > defaults`.
+    e.g. `vllm serve SOME_MODEL --config config.yaml`, SOME_MODEL takes precedence over `model` in config file.