ec/compal/ene932/acpi: Let mainboard define the ACPI lid object

The GP15 ACPI object was used to get the state of the lid. However
GP15 is specific to certain Intel chipsets, and will not always be in
the ACPI namespace. Instead of hardcoding this object, let the
mainboard define it.

Also, document the ACPI interface for the EC.

Change-Id: I02a2eb3116af61ea5701f84507327aa40218597a
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/5444
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Idwer Vollering <vidwer@gmail.com>
diff --git a/src/ec/compal/ene932/documentation.txt b/src/ec/compal/ene932/documentation.txt
new file mode 100644
index 0000000..eeb801a
--- /dev/null
+++ b/src/ec/compal/ene932/documentation.txt
@@ -0,0 +1,23 @@
+
+Accessing the EC space
+======================
+
+The ACPI implementation uses the standard I/O ports 0x62 and 0x66 to access the
+EC functionality. Accesses to these ports must be directed to the LPC bus to
+which the EC is connected.
+
+
+Interfacing with the ASL files
+==============================
+
+The mainboard code must define several variables for the ASL files.
+
+* EC_SCI
+  Defines the General Purpose Event (GPE) corresponding to the EC's SCI line.
+* EC_ACPI_LID_SWITCH_OBJECT
+  Defines the APCI object which reads the state of the lid, with 0 = open, and
+  1 = closed. This is usually the bit which reads the GPIO input corresponding
+  to the lid switch.
+* PNOT()
+  The mainboard must define a PNOT method to handle power state notifications
+  and Notify CPU device objects to re-evaluate their _PPC and _CST tables.