[PATCH v5] doc: improve e1000 driver documentation

[Talluri Chaitanyababu]

Add an overview of the e1000 driver for Intel 1G devices.

Signed-off-by: Talluri Chaitanyababu <chaitanyababux.talluri at intel.com>
---

v5:
* Aligned PMD names with code.
* Fixed wording for clarity.

v4:
* Fixed RST structure, single top-level title.
* Used ASCII "PCIe".
* Adjusted commit message to match content.

v3: Resolved apply patch failure.

v2: Addressed review comments.
---
 doc/guides/nics/e1000em.rst | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/doc/guides/nics/e1000em.rst b/doc/guides/nics/e1000em.rst
index ed4f57e9c6..a101b54020 100644
--- a/doc/guides/nics/e1000em.rst
+++ b/doc/guides/nics/e1000em.rst
@@ -4,7 +4,20 @@
 Driver for VM Emulated Devices
 ==============================
 
-The DPDK EM poll mode driver supports the following emulated devices:
+E1000 Poll Mode Driver
+----------------------
+
+DPDK provides several poll mode drivers (PMDs) supporting Intel 1 Gigabit ethernet controller families.
+These include:
+
+*   e1000_em – Intel 8254x family devices, including QEMU ``e1000`` emulation.
+*   e1000_igb – Intel PRO/1000 PCIe family.
+
+.. note::
+
+    The ``igb`` and ``igc`` PMDs are built from the same driver binary but are documented in separate sections for clarity.
+
+The e1000_em poll mode driver supports the following emulated devices:
 
 *   qemu-kvm emulated Intel® 82540EM Gigabit Ethernet Controller (qemu e1000 device)
 
-- 
2.43.0