docs: networking: convert x25.txt to ReST

Not much to be done here:
- add SPDX header;
- add a document title;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/Documentation/networking/index.rst b/Documentation/networking/index.rst
index 7a4bdbc..75521e6 100644
--- a/Documentation/networking/index.rst
+++ b/Documentation/networking/index.rst
@@ -116,6 +116,7 @@
    vrf
    vxlan
    x25-iface
+   x25
 
 .. only::  subproject and html
 
diff --git a/Documentation/networking/x25.txt b/Documentation/networking/x25.rst
similarity index 96%
rename from Documentation/networking/x25.txt
rename to Documentation/networking/x25.rst
index c91c6d7..00e45d3 100644
--- a/Documentation/networking/x25.txt
+++ b/Documentation/networking/x25.rst
@@ -1,4 +1,8 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================
 Linux X.25 Project
+==================
 
 As my third year dissertation at University I have taken it upon myself to
 write an X.25 implementation for Linux. My aim is to provide a complete X.25
diff --git a/net/x25/Kconfig b/net/x25/Kconfig
index a328f79..9f0d58b 100644
--- a/net/x25/Kconfig
+++ b/net/x25/Kconfig
@@ -20,7 +20,7 @@
 	  You can read more about X.25 at <http://www.sangoma.com/tutorials/x25/> and
 	  <http://docwiki.cisco.com/wiki/X.25>.
 	  Information about X.25 for Linux is contained in the files
-	  <file:Documentation/networking/x25.txt> and
+	  <file:Documentation/networking/x25.rst> and
 	  <file:Documentation/networking/x25-iface.rst>.
 
 	  One connects to an X.25 network either with a dedicated network card