[Model] Support SigLIP encoder and alternative decoders for LLaVA models (#7153)

Co-authored-by: Roger Wang <136131678+ywang96@users.noreply.github.com>

vllm/model_executor/models/__init__.py

@@ -1,6 +1,6 @@
 import functools
 import importlib
-from typing import Dict, List, Optional, Type
+from typing import Dict, List, Optional, Tuple, Type
 
 import torch.nn as nn
 
@@ -126,7 +126,7 @@ class ModelRegistry:
         return getattr(module, model_cls_name, None)
 
     @staticmethod
-    def load_model_cls(model_arch: str) -> Optional[Type[nn.Module]]:
+    def _try_load_model_cls(model_arch: str) -> Optional[Type[nn.Module]]:
         if model_arch in _OOT_MODELS:
             return _OOT_MODELS[model_arch]
         if model_arch not in _MODELS:
@@ -143,6 +143,18 @@ class ModelRegistry:
 
         return ModelRegistry._get_model(model_arch)
 
+    @staticmethod
+    def resolve_model_cls(
+            architectures: List[str]) -> Tuple[Type[nn.Module], str]:
+        for arch in architectures:
+            model_cls = ModelRegistry._try_load_model_cls(arch)
+            if model_cls is not None:
+                return (model_cls, arch)
+
+        raise ValueError(
+            f"Model architectures {architectures} are not supported for now. "
+            f"Supported architectures: {ModelRegistry.get_supported_archs()}")
+
     @staticmethod
     def get_supported_archs() -> List[str]:
         return list(_MODELS.keys())