Add submodule dependency filesHEADmaster

Change-Id: Iaf8d18082d3991dec7c0ebbea540f092188eb4ec

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diff --git a/roms/skiboot/doc/xscom-node-bindings.rst b/roms/skiboot/doc/xscom-node-bindings.rst
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+XSCOM Bindings
+==============
+
+XSCOM regions
+-------------
+
+The top-level xscom nodes specify the mapping range from the 64-bit address
+space into the PCB address space.
+
+There's one mapping range per chip xscom, therefore one node per mapping range.
+::
+
+ /
+ /xscom@<chip-base-address-0>/
+ /xscom@<chip-base-address-1>/
+ …
+ /xscom@<chip-base-address-n>/
+
+* where <chip-base-address-n> is the xscom base address with the gcid-specific
+  bits (for chip n) OR-ed in.
+
+Each xscom node has the following properties:
+
+ * #address-cells = 1
+ * #size-cells = 1
+ * reg = <base-address[#parent-address-cells] size[#parent-size-cells]>
+ * ibm,chip-id = gcid
+ * compatible = "ibm,xscom", "ibm,power8-scom" / "ibm,power7-xscom" 
+ * ecid = <Electronic Chip ID, applicable for POWER9 onwards>
+ * wafer-id = <wafer ID, applicable for POWER9 onwards>
+ * wafer-location = <wafer location, applicable for POWER9 onwards>
+
+ECID
+----
+Electronic Chip ID (ECID) is a process by which the wafer number, chip location
+(i.e. X,Y) and other optional data items are electrically encoded directly on
+the chip. wafer-id property represents wafer number and wafer-location property
+represents chip location (both X and Y location).
+
+
+Chiplet endpoints
+-----------------
+
+One sub-node per endpoint. Endpoints are defined by their (port,
+endpoint-address) data on the PCB, and are named according to their endpoint
+types:
+::
+
+ /xscom@<chip-base-address>/
+ /xscom@<chip-base-address>/chiptod@<endpoint-addr>
+ /xscom@<chip-base-address>/lpc@<endpoint-addr>
+
+* where the <endpoint-addr> is a single address (as distinct from the current
+  (gcid,base) format), consisting of the SCOM port and SCOM endpoint bits in
+  their 31-bit address format.
+
+Each endpoint node has the following properties:
+
+ * reg = <endpoint-address[#parent-address-cells] size[#parent-size-cells]>
+ * compatible - depends on endpoint type, eg "ibm,power8-chiptod" 
+
+The endpoint address specifies the address on the PCB. So, to calculate the
+MMIO address for a PCB register:
+::
+
+	mmio_addr  = <xscom-base-addr> | (pcb_addr[1:27] << 4)
+				       | (pcb_addr[28:31] << 3)
+
+Where:
+
+  * xscom-base-addr is the address from the first two cells of the parent
+    node's reg property
+  * pcb_addr is the first cell of the endpoint's reg property