nvidia-gpu: introduce notion of a device

Perform device discovery tasks only once per device to prepare for
introducing additional gpu sensors.

In the current implementation, sensor updates and device discovery via
MCTP are managed within a single class for simplicity. However, since a
GPU device typically includes multiple sensors, performing device
discovery for each individual sensor is inefficient. Instead, it would
be more effective to execute device discovery once per device.

Tested: Build an image for gb200nvl-obmc machine with the following
patches cherry picked. This patches are needed to enable the mctp stack.
https://gerrit.openbmc.org/c/openbmc/openbmc/+/79422

```
$ curl -k -u 'root:0penBmc' https://10.137.203.137/redfish/v1/Chassis/NVIDIA_GB200_1/Sensors/temperature_NVIDIA_GB200_GPU_0_TEMP_0
{
  "@odata.id": "/redfish/v1/Chassis/NVIDIA_GB200_1/Sensors/temperature_NVIDIA_GB200_GPU_0_TEMP_0",
  "@odata.type": "#Sensor.v1_2_0.Sensor",
  "Id": "temperature_NVIDIA_GB200_GPU_0_TEMP_0",
  "Name": "NVIDIA GB200 GPU 0 TEMP 0",
  "Reading": 37.6875,
  "ReadingRangeMax": 127.0,
  "ReadingRangeMin": -128.0,
  "ReadingType": "Temperature",
  "ReadingUnits": "Cel",
  "Status": {
    "Health": "OK",
    "State": "Enabled"
  }
}%
```

Change-Id: Ie3dcd43caa031b4aaa61d8be3f5d71aefd53bc9a
Signed-off-by: Harshit Aghera <haghera@nvidia.com>
diff --git a/src/nvidia-gpu/NvidiaDeviceDiscovery.hpp b/src/nvidia-gpu/NvidiaDeviceDiscovery.hpp
new file mode 100644
index 0000000..86211a9
--- /dev/null
+++ b/src/nvidia-gpu/NvidiaDeviceDiscovery.hpp
@@ -0,0 +1,42 @@
+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2024-2025 NVIDIA CORPORATION &
+ * AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include "MctpRequester.hpp"
+
+#include <boost/asio/io_context.hpp>
+#include <boost/container/flat_map.hpp>
+#include <sdbusplus/asio/connection.hpp>
+#include <sdbusplus/asio/object_server.hpp>
+#include <sdbusplus/message.hpp>
+
+#include <cstdint>
+#include <memory>
+#include <string>
+
+constexpr const char* sensorPathPrefix = "/xyz/openbmc_project/sensors/";
+constexpr const char* deviceType = "NvidiaMctpVdm";
+
+struct SensorConfigs
+{
+    std::string name;
+    uint64_t pollRate{};
+};
+
+class GpuDevice;
+
+void createSensors(
+    boost::asio::io_context& io, sdbusplus::asio::object_server& objectServer,
+    boost::container::flat_map<std::string, std::shared_ptr<GpuDevice>>&
+        gpuDevices,
+    const std::shared_ptr<sdbusplus::asio::connection>& dbusConnection,
+    mctp::MctpRequester& mctpRequester);
+
+void interfaceRemoved(
+    sdbusplus::message_t& message,
+    boost::container::flat_map<std::string, std::shared_ptr<GpuDevice>>&
+        gpuDevices);