Add README for eSim Microwatt integration flow

Signed-off-by: KirupaNithi <kirupanithi789@gmail.com>

esim/README.md

@@ -0,0 +1,61 @@
+# Microwatt eSim Integration
+
+## Overview
+
+This directory contains initial integration support for running the OpenPOWER Microwatt core inside the eSim/NGHDL co-simulation environment.
+
+The integration flow enables Microwatt to be compiled with GHDL and wrapped for NGHDL/XSPICE-based simulation inside eSim.
+
+## Files
+
+### `microwatt_cosim.vhdl`
+
+NGHDL-compatible wrapper for Microwatt.
+
+Exposed ports:
+
+* `clk` : Clock input
+* `rst` : Reset input
+* `uart_tx` : UART transmit output
+
+### `compile_for_nghdl.sh`
+
+Build script used to:
+
+* Compile Microwatt using GHDL
+* Build required helper objects
+* Elaborate the wrapper for NGHDL/XSPICE integration
+
+## Build Flow
+
+Run:
+
+```bash
+bash esim/compile_for_nghdl.sh
+```
+
+Successful compilation generates the NGHDL-compatible elaborated design.
+
+## eSim Workflow
+
+1. Compile Microwatt using the provided script
+2. Generate the NGHDL/XSPICE codemodel
+3. Import the generated block into eSim
+4. Create a schematic using:
+
+   * clock pulse
+   * reset pulse
+   * UART probe
+5. Run transient simulation
+
+## Current Status
+
+* Wrapper compilation successful
+* NGHDL integration validated
+* Basic schematic-level simulation setup completed
+
+## Future Work
+
+* Add memory and peripheral models
+* Expand validation workflows
+* Add example system-level designs