Minor fixes in the sample SDK add-on project.

Fixed the hardware.ini to remove an obsolete reference to the google add-on (copy/paste issue).
Added comments to the SDK add-on product makefile.
diff --git a/products/sample_addon.mk b/products/sample_addon.mk
index c0d66fe..ebf6cc7 100644
--- a/products/sample_addon.mk
+++ b/products/sample_addon.mk
@@ -1,13 +1,18 @@
+# List of apps and optional libraries (Java and native) to put in the add-on system image.
 PRODUCT_PACKAGES := \
 	PlatformLibraryClient \
 	com.example.android.platform_library \
 	libplatform_library_jni
 
+# Manually copy the optional library XML files in the system image.
 PRODUCT_COPY_FILES := \
     vendor/sample/frameworks/PlatformLibrary/com.example.android.platform_library.xml:system/etc/permissions/com.example.android.platform_library.xml
 
+# name of the add-on
 PRODUCT_SDK_ADDON_NAME := platform_library
 
+# Copy the manifest and hardware files for the SDK add-on.
+# The content of those files is manually created for now.
 PRODUCT_SDK_ADDON_COPY_FILES := \
     vendor/sample/sdk_addon/hardware.ini:hardware.ini \
     vendor/sample/sdk_addon/manifest.ini:manifest.ini
@@ -17,12 +22,19 @@
 # emulator skin (or for samples)
 #    $(call find-copy-subdir-files,*,development/emulator/skins/HVGA,skins/HVGA)
 
+# Copy the jar files for the optional libraries that are exposed as APIs.
 PRODUCT_SDK_ADDON_COPY_MODULES := \
     com.example.android.platform_library:libs/platform_library.jar
 
+# Name of the doc to generate and put in the add-on. This must match the name defined
+# in the optional library with the tag
+#    LOCAL_MODULE:= platform_library
+# in the documentation section.
 PRODUCT_SDK_ADDON_DOC_MODULE := platform_library
 
+# This add-on extends the default sdk product.
 $(call inherit-product, $(SRC_TARGET_DIR)/product/sdk.mk)
 
-# Overrides
+# Real name of the add-on. This is the name used to build the add-on.
+# Use 'make PRODUCT-<PRODUCT_NAME>-sdk_addon' to build the add-on.
 PRODUCT_NAME := sample_addon
diff --git a/sdk_addon/hardware.ini b/sdk_addon/hardware.ini
index e809bf5..c026136 100644
--- a/sdk_addon/hardware.ini
+++ b/sdk_addon/hardware.ini
@@ -1 +1 @@
-#no custom hardware setup for google add-ons
+#no custom hardware setup for the sample SDK add-on.