Add README.md files to the secureboot component

This commit adds a top-level README.md file to the secureboot
component that then calls into new README.md files in the different
sub-directories.

Change-Id: I7460a0e591232c2f8387321b0251ac3f62a1c76e
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/89025
Reviewed-by: Ilya Smirnov <ismirno@us.ibm.com>
Reviewed-by: Nicholas E Bofferding <bofferdn@us.ibm.com>
Reviewed-by: Christopher J Engel <cjengel@us.ibm.com>
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Daniel M Crowell <dcrowell@us.ibm.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/usr/secureboot/ext/README.md b/src/usr/secureboot/ext/README.md
new file mode 100644
index 000000000..797905b0d
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+++ b/src/usr/secureboot/ext/README.md
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+# **'ext'** Secureboot Services in Hostboot
+This directory implements additional (or 'extended') secureboot functionality
+ that is not considered part of the 'base' secureboot support.
+
+## Files
+
+* __makefile__
+  * Standard Hostboot makefile
+
+* __phys_presence.C__
+  * Implements the 'physical presence'-related functions, which are used to
+ assert that a system owner is physically present at the site of a system.
+    * This is done by using GPIO devices on the system's power button to
+ capture that the button was physically pressed.
+  * Functions are defined in
+ [phys_presence_if.H](../../../include/usr/secureboot/phys_presence_if.H)
+
+* __[README.md](./README.md)__
+  * This file
+
+* __service_ext.C__
+  * Implements some additional (or 'extended') functionality as defined in
+ [service_ext.H](../../../include/usr/secureboot/service_ext.H)
+