[PATCH] Features/Intel/Readme.md: clarify feature package dependency rule

["Ni, Ray" <ray.ni@intel.com>]

From: Ray Ni <niruiyu@users.noreply.github.com>

Original statement only says depending on another feature package
is not allowed. It gives developers impression that board level
packages are allowed to depend on.

This patch clarifies the package dependency rule.

Signed-off-by: Ray Ni <ray.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Amy Chan <amy.chan@intel.com>
Cc: Rangasai V Chaganty <rangasai.v.chaganty@intel.com>
Cc: Isaac W Oram <isaac.w.oram@intel.com>
---
 Features/Intel/Readme.md | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Features/Intel/Readme.md b/Features/Intel/Readme.md
index 9729f90a41..1a03a4c0d2 100644
--- a/Features/Intel/Readme.md
+++ b/Features/Intel/Readme.md
@@ -17,8 +17,10 @@ document as needed.
 ### Advanced Feature Attributes
 Advanced features should be:
 * _Cohesive_, the feature should not contain any functionality unrelated to the feature.
-* _Complete_, the feature must have a complete design that minimizes dependencies. A feature package cannot directly
-  depend on another feature package.
+* _Complete_, the feature must have a complete design that minimizes dependencies. A feature package can only depend
+  on following packages:
+  * edk2 repo: `MdePkg`, `MdeModulePkg`, `UefiCpuPkg`, `FmpDevicePkg`, `SecurityPkg`, `NetworkPkg`, `ShellPkg`.
+  * edk2-platforms repo: `MinPlatformPkg`, `IntelSiliconPkg`.
 * _Easy to Integrate_, the feature should expose well-defined software interfaces to use and configure the feature.
   * It should also present a set of simple and well-documented standard EDK II configuration options such as PCDs to
   configure the feature.
-- 
2.25.1