drm_hwcomposer: Add MediaTek platform support

This platform handler is dedicated for the i500 MediaTek SoC [1].
i500 has a Mali-G72 MP3 GPU.

OpenGL/Mali integration is based on ARM Gralloc module, version
BX304L01B-SW-99005-r20p0-01rel0, without additional patches.

This platformmediatek is based on platformmeson, without the additional
usage flag in the private_handle_t.
AFBC support has also been removed as it's unsupported.

External Android.bp file should be created in order to build this
module:

```
cc_library_shared {
    name: "hwcomposer.drm_mediatek",
    defaults: ["hwcomposer.drm_defaults"],
    srcs: [":drm_hwcomposer_platformmediatek"],
    whole_static_libs: ["drm_hwcomposer"],
}
```

[1] https://www.mediatek.com/products/AIoT/i500
Change-Id: I3ea7a980d76ba5c5ff583b5d4f21e1989875bafb
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
diff --git a/platform/platformmediatek.h b/platform/platformmediatek.h
new file mode 100644
index 0000000..61fcf47
--- /dev/null
+++ b/platform/platformmediatek.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#ifndef ANDROID_PLATFORM_MTK_H_
+#define ANDROID_PLATFORM_MTK_H_
+
+#include <hardware/gralloc.h>
+#include <stdatomic.h>
+
+#include "platform.h"
+#include "platformdrmgeneric.h"
+
+namespace android {
+
+class MediatekImporter : public DrmGenericImporter {
+ public:
+  using DrmGenericImporter::DrmGenericImporter;
+
+  int ConvertBoInfo(buffer_handle_t handle, hwc_drm_bo_t *bo) override;
+};
+}  // namespace android
+
+#endif