[PATCH v5 20/21] doc: update for txgbe guides

[Zaiyu Wang <zaiyuwang@trustnetic.com>]

Add new types of Wangxun NICs(Amber-Lite NIC models) into txgbe
supported NICs list, and supplement usage instructions.

Signed-off-by: Zaiyu Wang <zaiyuwang@trustnetic.com>
---
 doc/guides/nics/txgbe.rst | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/doc/guides/nics/txgbe.rst b/doc/guides/nics/txgbe.rst
index 93fb592759..3c741689a7 100644
--- a/doc/guides/nics/txgbe.rst
+++ b/doc/guides/nics/txgbe.rst
@@ -4,8 +4,12 @@
 TXGBE Poll Mode Driver
 ======================
 
-The TXGBE PMD (librte_pmd_txgbe) provides poll mode driver support
-for Wangxun 10 Gigabit Ethernet NICs.
+Supported NICs
+--------------
+
+- Wangxun 10 Gigabit Ethernet NICs
+- Wangxun 25 Gigabit Ethernet NICs
+- Wangxun 40 Gigabit Ethernet NICs
 
 Features
 --------
@@ -30,6 +34,7 @@ Features
 - FW version
 - LRO
 - Generic flow API
+- Forward Error Correction (FEC) (only for 25G NICs)
 
 Prerequisites
 -------------
@@ -37,6 +42,9 @@ Prerequisites
 - Learning about Wangxun 10 Gigabit Ethernet NICs using
   `<https://www.net-swift.com/a/383.html>`_.
 
+- Learning about Wangxun 25 Gigabit Ethernet NICs using
+  `<https://www.net-swift.com/a/25GbE-tong-yong-lei-FF5025.html>`_.
+
 - Follow the DPDK :ref:`Getting Started Guide for Linux <linux_gsg>` to setup the basic DPDK environment.
 
 Configuration
@@ -139,6 +147,25 @@ Please note that following ``devargs`` are only set for backplane NICs.
   PHY parameter used for user debugging. Setting other values to
   take effect requires setting the ``ffe_set``.
 
+Please note that following ``devargs`` are only set for Amber-Lite NICs.
+
+- ``tx_headwb`` (default **1**)
+
+  Use to enable the TX Head Write-Back mode. In this mode, the hardware
+  merges and writes back a group of TX descriptors together to reduce
+  memory access times, which helps improve performance.
+
+- ``tx_headwb_size`` (default **16**)
+
+  Tx head write-back length. It is recommended to use the default values.
+  Setting other values to take effect requires setting the ``tx_headwb``.
+
+- ``rx_desc_merge`` (default **1**)
+
+  Use to enable the RX descriptor merge mode. In this mode, the hardware
+  merges and writes back a group of RX descriptors together to reduce
+  memory access times, which helps improve performance.
+
 Driver compilation and testing
 ------------------------------
 
-- 
2.21.0.windows.1