Change filename personalize.py to patch_uds_udi.py

Also adding a more detailed explaination of what the script intends to
do

hw/application_fpga/tools/patch_uds_udi.py

@@ -1,17 +1,34 @@
 # -*- coding: utf-8 -*-
 #=======================================================================
 #
-# personalize.py
+# Copyright (C) 2023 Tillitis AB
+# Written by Myrtle Shah <gatecat@ds0.me>
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# patch_uds_udi.py
 # --------------
 # Python program that patches the UDS and UDI implemented using
 # named LUT4 instances to have unique initial values, not the generic
 # values used during synthesis, p&r and mapping. This allows us to
 # generate device unique bitstreams without running the complete flow.
 #
+# Both the UDI and UDS are using bit indexing from 32 LUTs for each
+# word, i.e., the first word consists of bit 0 from each 32 LUTs and
+# so on.
+#
+# The size requirements for the UDI and UDS are specified as 1 bit (8
+# bytes of data) and 3 bits (32 bytes of data), respectively. The UDI
+# does not occupy the entire LUT4 instance, and to conserve resources,
+# the pattern of the UDI is repeated over the unused portion of the
+# LUT4 instance. This eliminates the need to drive the three MSB pins
+# while still achieving the correct output.
+#
+# In the case of UDS, a read-enable signal is present, and the most
+# significant bit serves as the read-enable input. This requires the
+# lower half of initialization bits to be forced to zero, ensuring
+# that the memory outputs zero when the read-enable signal is
+# inactive.
 #
-# Copyright (C) 2023 Tillitis AB
-# Written by Myrtle Shah <gatecat@ds0.me>
-# SPDX-License-Identifier: GPL-2.0-only
 #
 #=======================================================================