[SYCL][DOC] Clarify device global error conditions (#4972)

Clarify the behavior of `handler::copy()` and `handler::memcpy()` in
two error cases w.r.t `device_global` variables.

sycl/doc/extensions/DeviceGlobal/SYCL_INTEL_device_global.asciidoc

@@ -947,6 +947,14 @@ Not available if `PropertyListT` contains the `host_access` property with
 `read` or `none` assertions.
 
 Copies _count_ elements of type `std::remove_all_extents_t<T>` from the pointer _src_ to the `device_global` _dest_, starting at _startIndex_ elements of _dest_. _src_ may be either a host or USM pointer.
+
+If _count_ and _startIndex_ would cause data to be written beyond the end of
+the variable _dest_, the implementation throws an `exception` with the
+`errc::invalid` error code.
+
+If `PropertyListT` contains the `device_image_scope` property and the _dest_
+variable exists in more than one _device image_ for this queue's device, the
+implementation throws an `exception` with the `errc::invalid` error code.
 a| 
 [source, c++]
 ----
@@ -963,6 +971,14 @@ Not available if `PropertyListT` contains the `host_access` property with
 
 Copies _count_ elements of type `std::remove_all_extents_t<T>` from the `device_global` _src_ to the pointer _dest_, starting at _startIndex_ elements of _src_. _dest_ may be either a host or USM pointer.
 
+If _count_ and _startIndex_ would cause data to be read beyond the end of
+the variable _src_, the implementation throws an `exception` with the
+`errc::invalid` error code.
+
+If `PropertyListT` contains the `device_image_scope` property and the _src_
+variable exists in more than one _device image_ for this queue's device, the
+implementation throws an `exception` with the `errc::invalid` error code.
+
 a| 
 [source, c++]
 ----
@@ -977,6 +993,14 @@ Not available if `PropertyListT` contains the `host_access` property with
 
 Copies _count_ bytes from the pointer _src_ to the `device_global` _dest_, starting at _offset_ bytes. _src_ may be either a host or USM pointer.
 
+If _numBytes_ and _offset_ would cause data to be written beyond the end of
+the variable _dest_, the implementation throws an `exception` with the
+`errc::invalid` error code.
+
+If `PropertyListT` contains the `device_image_scope` property and the _dest_
+variable exists in more than one _device image_ for this queue's device, the
+implementation throws an `exception` with the `errc::invalid` error code.
+
 a| 
 [source, c++]
 ----
@@ -991,9 +1015,28 @@ Not available if `PropertyListT` contains the `host_access` property with
 `write` or `none` assertions.
 
 Copies _count_ bytes from the `device_global` _src_ to the pointer _dest_, starting at _offset_ bytes. _dest_ may be either a host or USM pointer.
+
+If _numBytes_ and _offset_ would cause data to be read beyond the end of
+the variable _src_, the implementation throws an `exception` with the
+`errc::invalid` error code.
+
+If `PropertyListT` contains the `device_image_scope` property and the _src_
+variable exists in more than one _device image_ for this queue's device, the
+implementation throws an `exception` with the `errc::invalid` error code.
 |====
 --
 
+[NOTE]
+====
+As specified above, the `copy` and `memcpy` functions throw an exception if the
+global variable has the `device_image_scope` property and exists in more than
+one _device image_ for the queue's device.  This condition could occur if the
+application submits a kernel referencing the variable to the same device with
+different values for a specialization constant (when the device supports
+specialization constants natively).  This condition could also occur if the
+application submits the same kernel from more than one kernel bundle.
+====
+
 
 == Non-normative: Future anticipated changes, not enabled within this version of the specification