Update release notes

Author: FrancescAlted

RELEASE_NOTES.md

@@ -1,11 +1,43 @@
-Release notes for C-Blosc2 2.2.1
+Release notes for C-Blosc2 2.3.0
 ================================
 
-Changes from 2.2.0 to 2.2.1
+Changes from 2.2.0 to 2.3.0
 ===========================
 
-#XXX version-specific blurb XXX#
-
+* [API change] In order to allow to compile with both C-Blosc and C-Blosc2 libraries, a new API has been created for the symbols and function names that had collisions.  Here are the changed symbols and functions:
+
+  * Blosc2 symbols that take different values than in Blosc1:
+    - BLOSC_MAX_OVERHEAD -> BLOSC2_MAX_OVERHEAD
+    - BLOSC_MAX_BUFFERSIZE -> BLOSC2_MAX_BUFFERSIZE
+
+  * Original Blosc1 API that takes the `blosc1_` prefix:
+    - blosc_compress -> blosc1_compress
+    - blosc_decompress -> blosc1_decompress
+    - blosc_getitem -> blosc1_getitem
+    - blosc_get_compressor -> blosc1_get_compressor
+    - blosc_set_compressor -> blosc_set_compressor
+    - blosc_cbuffer_sizes -> blosc1_cbuffer_sizes
+    - blosc_cbuffer_validate -> blosc1_cbuffer_validate
+    - blosc_cbuffer_metainfo -> blosc1_cbuffer_metainfo
+    - blosc_get_blocksize -> blosc1_get_blocksize
+    - blosc_set_blocksize -> blosc1_set_blocksize
+    - blosc_set_splitmode -> blosc1_set_splitmode
+
+  * API that has been migrated to blosc2_ prefix
+    - blosc_init -> blosc2_init
+    - blosc_destroy -> blosc2_destroy
+    - blosc_free_resources -> blosc2_free_resources
+    - blosc_get_nthreads -> blosc2_get_nthreads
+    - blosc_set_nthreads -> blosc2_set_nthreads
+    - blosc_compcode_to_compname -> blosc2_compcode_to_compname
+    - blosc_compname_to_compcode -> blosc2_compname_to_compcode
+    - blosc_list_compressors -> blosc2_list_compressors
+    - blosc_get_version_string -> blosc2_get_version_string
+    - blosc_get_complib_info -> blosc2_get_complib_info
+    - blosc_cbuffer_versions -> blosc2_cbuffer_versions
+    - blosc_cbuffer_complib -> blosc2_cbuffer_complib
+
+  To compile with the previous API (corresponding to C-Blosc2 pre-2.3.0), it is enough to define the `BLOSC1_COMPAT` symbol in your C-Blosc2 app.
 
 Changes from 2.1.1 to 2.2.0
 ===========================