Create Documentation/security/,

move LSM-, credentials-, and keys-related files from Documentation/
  to Documentation/security/,
add Documentation/security/00-INDEX, and
update all occurrences of Documentation/<moved_file>
  to Documentation/security/<moved_file>.

Documentation/security/00-INDEX

@@ -0,0 +1,18 @@
+00-INDEX
+	- this file.
+SELinux.txt
+	- how to get started with the SELinux security enhancement.
+Smack.txt
+	- documentation on the Smack Linux Security Module.
+apparmor.txt
+	- documentation on the AppArmor security extension.
+credentials.txt
+	- documentation about credentials in Linux.
+keys-request-key.txt
+	- description of the kernel key request service.
+keys-trusted-encrypted.txt
+	- info on the Trusted and Encrypted keys in the kernel key ring service.
+keys.txt
+	- description of the kernel key retention service.
+tomoyo.txt
+	- documentation on the TOMOYO Linux Security Module.