[circle-mlir/import] Introduce CircleImport

This will introduce CircleImport to import circle mode files.
Code itself is from Tensorflow flatbuffer_import.cc with little
modification and removed that are not necessary at this moment.

ONE-DCO-1.0-Signed-off-by: SaeHie Park <[email protected]>

circle-mlir/circle-mlir/lib/import/CMakeLists.txt

@@ -1,4 +1,5 @@
 set(SRC
+  src/CircleImport.cpp
   src/CircleOperator.cpp
 )
 

circle-mlir/circle-mlir/lib/import/include/circle-mlir/import/CircleImport.h

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2025 Samsung Electronics Co., Ltd. All Rights Reserved
+ * Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// from tensorflow/compiler/mlir/lite/flatbuffer_import.h
+
+#ifndef __CIRCLE_MLIR_IMPORT_CIRCLE_IMPORT_H__
+#define __CIRCLE_MLIR_IMPORT_CIRCLE_IMPORT_H__
+
+#include <string>
+#include <vector>
+
+#include <absl/strings/string_view.h>
+#include <mlir/Dialect/Func/IR/FuncOps.h>
+#include <mlir/IR/BuiltinOps.h>
+#include <mlir/IR/Location.h>
+#include <mlir/IR/MLIRContext.h>
+
+namespace mlir
+{
+namespace Circle
+{
+
+mlir::OwningOpRef<mlir::ModuleOp>
+FlatBufferToMlir(absl::string_view buffer, mlir::MLIRContext *context, mlir::Location base_loc,
+                 bool use_external_constant = false,
+                 const std::vector<std::string> &ordered_input_arrays = {},
+                 const std::vector<std::string> &ordered_output_arrays = {},
+                 bool experimental_prune_unreachable_nodes_unconditionally = false);
+
+} // namespace Circle
+} // namespace mlir
+
+#endif // __CIRCLE_MLIR_IMPORT_CIRCLE_IMPORT_H__