Add README.md for the NXP eIQ Neutron Backend (#9718)

### Summary
Initial Readme, introducing the NXP's eIQ Neutron Backend, supporting
the eIQ Neutron NPU hardware accelerator.

Author: robert-kalmar

backends/nxp/README.md

@@ -0,0 +1,44 @@
+# NXP eIQ Neutron Backend
+
+This subtree contains the ExecuTorch Backend implementation for the
+[eIQ® Neutron Neural Processing Unit (NPU)](https://www.nxp.com/applications/technologies/ai-and-machine-learning/eiq-neutron-npu:EIQ-NEUTRON-NPU).
+
+The eIQ® Neutron NPU is a highly scalable accelerator core architecture providing machine learning (ML) acceleration,
+able to support common and critical tasks for edge AI such as anomaly detection, speech recognition,
+image classification, object detection, facial recognition, image segmentation, and generative AI use cases like 
+large and small language models (LLMs & SLMs) and text-to-speech (TTS).
+The architecture provides power and performance optimized NPUs integrated with NXP's broad portfolio of 
+microcontrollers and applications processors.
+
+The eIQ Neutron NPUs offer support for a wide variety of neural network types such as CNN, RNN, TCN and Transformer 
+networks, as well as the ability to adapt and scale to new model architectures, topologies and layer types introduced
+to AI workloads. ML application development with the eIQ Neutron NPU is fully supported by the 
+[eIQ machine learning software development environment](https://www.nxp.com/design/design-center/software/eiq-ml-development-environment/eiq-toolkit-for-end-to-end-model-development-and-deployment:EIQ-TOOLKIT).
+The eIQ AI SW Stack provides a streamlined development experience for developers and end-users of NXP products.
+eIQ extensions connect broader AI ecosystems to the edge, such as the NVIDIA TAO extension, which enables developers to bring AI models trained and fine-tuned with TAO to NXP-powered edge devices.
+
+
+## Supported NXP platforms
+At this moment following eIQ® Neutron NPU variants and NXP platforms are supported by the NXP eIQ Neutron Backend:
+
+* **eIQ Neutron N3-64**, available on [i.MX RT700](https://www.nxp.com/products/i.MX-RT700)
+
+In the future the NXP eIQ Neutron Backend will be extended to support [i.MX 9 Application Processors](https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/i-mx-applications-processors/i-mx-9-processors:IMX9-PROCESSORS) 
+with eIQ Neutron NPU, like the [i.MX 95](https://www.nxp.com/products/iMX95).
+
+
+## Layout
+TBD
+
+## Backend Status and Maturity
+**Current Status:** Prototype Quality
+
+The eIQ Neutron NPU Backend should be considered as prototype quality at this moment. Subject to significant changes and 
+improvements. NXP and the ExecuTorch community is actively developing this codebase. 
+
+## Help & Improvements
+If you have problems or questions or have suggestions for ways to make
+implementation and testing better, please reach out to the NXP representative for the SoC you are interested in using,
+or your distribution partner contact.
+
+Or raise the issue here on ExecuTorch GitHub, label it with `module: nxp` and our ML team will address it on a priority-basis.