[MUSA][4/N] Add common device utilities, distributed backend, and custom op wiring (#17246)

Signed-off-by: Xiaodong Ye <xiaodong.ye@mthreads.com>

python/sglang/multimodal_gen/runtime/layers/custom_op.py

@@ -53,6 +53,12 @@ class CustomOp(nn.Module):
         # NOTE(woosuk): This is a placeholder for future extensions.
         return self.forward_native(*args, **kwargs)
 
+    def forward_musa(self, *args, **kwargs) -> Any:
+        # XXX (MUSA): MUSA kernels follow the CUDA path by default.
+        # At this stage, sgl-kernel support for MUSA is still under active
+        # development, so we fall back to the PyTorch-native implementation.
+        return self.forward_native(*args, **kwargs)
+
     def forward_oot(self, *args, **kwargs) -> Any:
         # By default, we assume that OOT ops are compatible with the
         # PyTorch-native implementation.
@@ -67,6 +73,8 @@ class CustomOp(nn.Module):
             return self.forward_npu
         elif current_platform.is_xpu():
             return self.forward_xpu
+        elif current_platform.is_musa():
+            return self.forward_musa
         else:
             return self.forward_native